diff --git a/.tx/config b/.tx/config
index cacd073fa4f28..bc18d862ea8b3 100644
--- a/.tx/config
+++ b/.tx/config
@@ -205,3 +205,9 @@ file_filter = translationfiles/<lang>/workflowengine.po
 source_file = translationfiles/templates/workflowengine.pot
 source_lang = en
 type        = PO
+
+[o:nextcloud:p:nextcloud:r:viewer]
+file_filter = translationfiles/<lang>/viewer.po
+source_file = translationfiles/templates/viewer.pot
+source_lang = en
+type        = PO
diff --git a/REUSE.toml b/REUSE.toml
index 2904855498246..9c15d59740004 100644
--- a/REUSE.toml
+++ b/REUSE.toml
@@ -356,3 +356,4 @@ path = "core/img/libreoffice.svg"
 precedence = "aggregate"
 SPDX-FileCopyrightText = "2011-2026 The Document Foundation"
 SPDX-License-Identifier = "LicenseRef-TheDocumentFoundationTrademarks"
+
diff --git a/apps/files/lib/Controller/ViewController.php b/apps/files/lib/Controller/ViewController.php
index 054bb106e150f..f53dc3d9c2713 100644
--- a/apps/files/lib/Controller/ViewController.php
+++ b/apps/files/lib/Controller/ViewController.php
@@ -17,7 +17,6 @@
 use OCA\Files\Event\LoadSidebar;
 use OCA\Files\Service\UserConfig;
 use OCA\Files\Service\ViewConfig;
-use OCA\Viewer\Event\LoadViewer;
 use OCP\App\IAppManager;
 use OCP\AppFramework\Controller;
 use OCP\AppFramework\Http\Attribute\NoAdminRequired;
@@ -198,9 +197,6 @@ public function index($dir = '', $view = '', $fileid = null) {
 		$this->eventDispatcher->dispatchTyped(new LoadSidebar());
 		$this->eventDispatcher->dispatchTyped(new LoadSearchPlugins());
 		// Load Viewer scripts
-		if (class_exists(LoadViewer::class)) {
-			$this->eventDispatcher->dispatchTyped(new LoadViewer());
-		}
 
 		$this->initialState->provideInitialState('templates_enabled', true);
 		$this->initialState->provideInitialState('templates_path', $this->templateManager->hasTemplateDirectory() ? $this->templateManager->getTemplatePath() : false);
diff --git a/apps/files/src/actions/openLocallyAction.ts b/apps/files/src/actions/openLocallyAction.ts
index 963df49e44442..667928ebda75b 100644
--- a/apps/files/src/actions/openLocallyAction.ts
+++ b/apps/files/src/actions/openLocallyAction.ts
@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
-import type { IFileAction } from '@nextcloud/files'
+import type { ActionContextSingle, IFile, IFileAction, INode } from '@nextcloud/files'
 
 import LaptopSvg from '@mdi/svg/svg/laptop.svg?raw'
 import IconWeb from '@mdi/svg/svg/web.svg?raw'
@@ -15,6 +15,7 @@ import { translate as t } from '@nextcloud/l10n'
 import { encodePath } from '@nextcloud/paths'
 import { generateOcsUrl } from '@nextcloud/router'
 import { isPublicShare } from '@nextcloud/sharing/public'
+import { getViewer } from '@nextcloud/viewer'
 import { logger } from '../utils/logger.ts'
 import { isSyncable } from '../utils/permissions.ts'
 
@@ -44,8 +45,8 @@ export const action: IFileAction = {
 		return isSyncable(nodes[0]!)
 	},
 
-	async exec({ nodes }) {
-		await attemptOpenLocalClient(nodes[0].path)
+	async exec({ nodes, contents }) {
+		await attemptOpenLocalClient(nodes[0], contents)
 		return null
 	},
 
@@ -60,15 +61,16 @@ export const action: IFileAction = {
  * 2. Open online: The viewer is used to open the file.
  * 3. Close the dialog and nothing happens (abort).
  *
- * @param path - The path to open
+ * @param node - The file to open
+ * @param contents - The folder the file is in, so the viewer can navigate
  */
-async function attemptOpenLocalClient(path: string) {
-	await openLocalClient(path)
+async function attemptOpenLocalClient(node: INode, contents: ActionContextSingle['contents']) {
+	await openLocalClient(node.path)
 	const result = await confirmLocalEditDialog()
 	if (result === 'local') {
-		await openLocalClient(path)
+		await openLocalClient(node.path)
 	} else if (result === 'online') {
-		window.OCA.Viewer.open({ path })
+		await getViewer().open(contents as IFile[], node as IFile)
 	}
 }
 
diff --git a/apps/files_sharing/lib/DefaultPublicShareTemplateProvider.php b/apps/files_sharing/lib/DefaultPublicShareTemplateProvider.php
index af755fc0eb444..7e2091d23cba4 100644
--- a/apps/files_sharing/lib/DefaultPublicShareTemplateProvider.php
+++ b/apps/files_sharing/lib/DefaultPublicShareTemplateProvider.php
@@ -11,7 +11,6 @@
 use OCA\FederatedFileSharing\FederatedShareProvider;
 use OCA\Files_Sharing\AppInfo\Application;
 use OCA\Files_Sharing\Event\BeforeTemplateRenderedEvent;
-use OCA\Viewer\Event\LoadViewer;
 use OCP\Accounts\IAccountManager;
 use OCP\AppFramework\Http\ContentSecurityPolicy;
 use OCP\AppFramework\Http\Template\ExternalShareMenuAction;
@@ -118,11 +117,6 @@ public function renderPage(IShare $share, string $token, string $path): Template
 		$isFileRequest = $attributes?->getAttribute('fileRequest', 'enabled') === true;
 		$this->initialState->provideInitialState('isFileRequest', $isFileRequest);
 
-		// Load Viewer scripts
-		if (class_exists(LoadViewer::class)) {
-			$this->eventDispatcher->dispatchTyped(new LoadViewer());
-		}
-
 		$this->initialState->provideInitialState('templates', $this->templateManager->listCreators());
 
 		// Allow external apps to register their scripts
diff --git a/apps/files_versions/src/utils/versions.spec.ts b/apps/files_versions/src/utils/versions.spec.ts
new file mode 100644
index 0000000000000..b80f9579d2554
--- /dev/null
+++ b/apps/files_versions/src/utils/versions.spec.ts
@@ -0,0 +1,99 @@
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { INode } from '@nextcloud/files'
+import type { Version } from './versions.ts'
+
+import { File, Permission } from '@nextcloud/files'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('@nextcloud/auth', async (orig) => {
+	// eslint-disable-next-line @typescript-eslint/consistent-type-imports -- vitest importOriginal idiom
+	const actual = await orig<typeof import('@nextcloud/auth')>()
+	return {
+		...actual,
+		getCurrentUser: () => ({ uid: 'alice', displayName: 'Alice', isAdmin: false }),
+	}
+})
+
+const { versionToNode } = await import('./versions.ts')
+
+/**
+ * Build the file a version belongs to.
+ */
+function makeNode(): INode {
+	return new File({
+		id: 42,
+		source: 'https://cloud.example.com/remote.php/dav/files/alice/holiday.jpg',
+		root: '/files/alice',
+		owner: 'alice',
+		mime: 'image/jpeg',
+		mtime: new Date('2025-01-22T11:20:00Z'),
+	})
+}
+
+/**
+ * Build a version of that file, as fetchVersions returns them.
+ *
+ * @param overrides - Fields to override on the version
+ */
+function makeVersion(overrides: Partial<Version> = {}): Version {
+	return {
+		fileId: '42',
+		label: '',
+		author: 'alice',
+		authorName: 'Alice',
+		filename: '/versions/alice/versions/42/1737542400',
+		basename: '22 January 2025, 11:20:00',
+		mime: 'image/jpeg',
+		etag: 'abc123',
+		size: 1024,
+		type: 'file',
+		mtime: 1737542400000,
+		permissions: 'R',
+		previewUrl: 'https://cloud.example.com/apps/files_versions/preview?file=/holiday.jpg&version=1737542400',
+		url: '/remote.php/dav/versions/alice/versions/42/1737542400',
+		source: 'https://cloud.example.com/remote.php/dav/versions/alice/versions/42/1737542400',
+		fileVersion: '1737542400',
+		...overrides,
+	} as Version
+}
+
+describe('versionToNode', () => {
+	let node: INode
+
+	beforeEach(() => {
+		node = makeNode()
+	})
+
+	it('points at the version content rather than at its thumbnail', () => {
+		const version = versionToNode(makeVersion(), node)
+
+		expect(version.source).toBe('https://cloud.example.com/remote.php/dav/versions/alice/versions/42/1737542400')
+		// The version preview is a 250px thumbnail meant for the list, so the
+		// viewer has to load the version itself
+		expect(version.attributes.hasPreview).toBe(false)
+	})
+
+	it('reads as the date it was taken, not as its id on the server', () => {
+		const version = versionToNode(makeVersion(), node)
+
+		expect(version.basename).toBe('1737542400')
+		expect(version.displayname).toBe('22 January 2025, 11:20:00')
+	})
+
+	it('is read-only, whatever the file it belongs to allows', () => {
+		const version = versionToNode(makeVersion(), node)
+
+		expect(version.permissions).toBe(Permission.READ)
+	})
+
+	it('takes the mime of the file when the version reports none', () => {
+		// The current version comes back with an empty mime
+		const version = versionToNode(makeVersion({ mime: '' }), node)
+
+		expect(version.mime).toBe('image/jpeg')
+	})
+})
diff --git a/apps/files_versions/src/utils/versions.ts b/apps/files_versions/src/utils/versions.ts
index 77995e85d7677..451de38eada99 100644
--- a/apps/files_versions/src/utils/versions.ts
+++ b/apps/files_versions/src/utils/versions.ts
@@ -8,6 +8,7 @@ import type { FileStat, ResponseDataDetailed } from 'webdav'
 
 import { getCurrentUser } from '@nextcloud/auth'
 import axios from '@nextcloud/axios'
+import { File, Permission } from '@nextcloud/files'
 import { getClient } from '@nextcloud/files/dav'
 import { getCanonicalLocale } from '@nextcloud/l10n'
 import { encodePath, join } from '@nextcloud/paths'
@@ -36,6 +37,39 @@ export interface Version {
 
 const client = getClient()
 
+/**
+ * Build a node for a version, so that it can be handed to the viewer.
+ *
+ * The version content lives at its own dav endpoint, which is what the
+ * node points at: the preview a version has is a 250px thumbnail meant
+ * for this list, too small to show as the file itself. A version is
+ * named after its id on the server and reads as the date it was taken,
+ * so that is its display name.
+ *
+ * @param version - The version to build a node for
+ * @param node - The file the version belongs to
+ */
+export function versionToNode(version: Version, node: INode): File {
+	const owner = getCurrentUser()?.uid ?? null
+
+	return new File({
+		id: Number(version.fileId),
+		source: version.source,
+		root: `/versions/${owner}/versions/${version.fileId}`,
+		displayname: version.basename,
+		// The current version reports no mime of its own
+		mime: version.mime || node.mime || 'application/octet-stream',
+		size: version.size,
+		mtime: new Date(version.mtime),
+		owner,
+		permissions: Permission.READ,
+		attributes: {
+			etag: version.etag,
+			hasPreview: false,
+		},
+	})
+}
+
 /**
  * Get file versions for a given node
  *
diff --git a/apps/files_versions/src/views/FilesVersionsSidebarTab.vue b/apps/files_versions/src/views/FilesVersionsSidebarTab.vue
index ee4f11a3e8397..8c9cadddb29b8 100644
--- a/apps/files_versions/src/views/FilesVersionsSidebarTab.vue
+++ b/apps/files_versions/src/views/FilesVersionsSidebarTab.vue
@@ -41,12 +41,13 @@
 </template>
 
 <script lang="ts" setup>
-import type { IFolder, INode, IView } from '@nextcloud/files'
+import type { IFile, IFolder, INode, IView } from '@nextcloud/files'
 import type { Version } from '../utils/versions.ts'
 
 import { showError, showSuccess } from '@nextcloud/dialogs'
 import { emit } from '@nextcloud/event-bus'
 import { t } from '@nextcloud/l10n'
+import { getViewer, canView as viewerCanView } from '@nextcloud/viewer'
 import { useIsMobile } from '@nextcloud/vue/composables/useIsMobile'
 import { watchDebounced } from '@vueuse/core'
 import { computed, ref, watch } from 'vue'
@@ -55,7 +56,7 @@ import VersionEntry from '../components/VersionEntry.vue'
 import VersionLabelDialog from '../components/VersionLabelDialog.vue'
 import VirtualScrolling from '../components/VirtualScrolling.vue'
 import logger from '../utils/logger.ts'
-import { deleteVersion, fetchVersions, restoreVersion, setVersionLabel } from '../utils/versions.ts'
+import { deleteVersion, fetchVersions, restoreVersion, setVersionLabel, versionToNode } from '../utils/versions.ts'
 
 const props = defineProps<{
 	active: boolean
@@ -114,18 +115,10 @@ const initialVersionMtime = computed(() => {
 		.reduce((a, b) => Math.min(a, b))
 })
 
-const canView = computed(() => {
-	if (!props.node) {
-		return false
-	}
+const canView = computed(() => props.node !== null && viewerCanView(props.node))
 
-	return window.OCA.Viewer?.mimetypes?.includes(props.node?.mime)
-})
-
-const canCompare = computed(() => {
-	return !isMobile.value
-		&& window.OCA.Viewer?.mimetypesCompare?.includes(props.node?.mime)
-})
+// Comparison puts the two files side by side, which needs the width for it
+const canCompare = computed(() => !isMobile.value && canView.value)
 
 // When either the current node to show or its mtime changes we need to refetch the versions
 // When the id changed we immediately show changes
@@ -247,41 +240,23 @@ function openVersion(version: Version) {
 		return
 	}
 
-	// Open current file view instead of read only
-	if (version.mtime === props.node?.mtime?.getTime()) {
-		window.OCA.Viewer.open({ path: props.node.path })
+	// The newest version is the file itself, which opens as it normally would
+	if (version.mtime === props.node.mtime?.getTime()) {
+		getViewer().open([props.node as IFile], props.node as IFile)
 		return
 	}
 
-	window.OCA.Viewer.open({
-		fileInfo: {
-			...version,
-			// Versions previews are too small for our use case, so we override previewUrl
-			// to either point to the original file or original version.
-			filename: version.filename,
-			previewUrl: undefined,
-		},
-		enableSidebar: false,
-	})
+	// The sidebar resolves a file by its dav source and a version is not
+	// one it can find there
+	const versionNode = versionToNode(version, props.node)
+	getViewer().open([versionNode], versionNode, { enableSidebar: false })
 }
 
 /**
  * @param version - The version to compare
  */
 function compareVersion(version: Version) {
-	const _versions = versions.value.map((version) => ({ ...version, previewUrl: undefined }))
-
-	window.OCA.Viewer.compare(
-		{
-			fileid: props.node!.fileid,
-			filename: props.node!.path,
-			basename: props.node!.basename,
-			source: props.node!.source,
-			mime: props.node!.mime,
-			hasPreview: props.node!.attributes?.['has-preview'] ?? false,
-		},
-		_versions.find((v) => v.source === version.source),
-	)
+	getViewer().compare(props.node as IFile, versionToNode(version, props.node))
 }
 </script>
 
diff --git a/apps/settings/lib/Settings/Personal/ServerDevNotice.php b/apps/settings/lib/Settings/Personal/ServerDevNotice.php
index f4c4f04a33ba4..b0b6c7cf22047 100644
--- a/apps/settings/lib/Settings/Personal/ServerDevNotice.php
+++ b/apps/settings/lib/Settings/Personal/ServerDevNotice.php
@@ -7,10 +7,8 @@
 
 namespace OCA\Settings\Settings\Personal;
 
-use OCA\Viewer\Event\LoadViewer;
 use OCP\AppFramework\Http\TemplateResponse;
 use OCP\AppFramework\Services\IInitialState;
-use OCP\EventDispatcher\IEventDispatcher;
 use OCP\Files\IRootFolder;
 use OCP\IURLGenerator;
 use OCP\IUserSession;
@@ -22,7 +20,6 @@ class ServerDevNotice implements ISettings {
 
 	public function __construct(
 		private IRegistry $registry,
-		private IEventDispatcher $eventDispatcher,
 		private IRootFolder $rootFolder,
 		private IUserSession $userSession,
 		private IInitialState $initialState,
@@ -39,12 +36,9 @@ public function getForm(): TemplateResponse {
 
 		$hasInitialState = false;
 
-		// If the Reasons to use Nextcloud.pdf file is here, let's init Viewer, also check that Viewer is there
-		if (class_exists(LoadViewer::class) && $userFolder->nodeExists('Reasons to use Nextcloud.pdf')) {
-			/**
-			 * @psalm-suppress UndefinedClass, InvalidArgument
-			 */
-			$this->eventDispatcher->dispatch(LoadViewer::class, new LoadViewer());
+		// The viewer loads itself; this only decides whether the notice has
+		// a file to point at
+		if ($userFolder->nodeExists('Reasons to use Nextcloud.pdf')) {
 			$hasInitialState = true;
 		}
 
diff --git a/apps/settings/src/main-nextcloud-pdf.js b/apps/settings/src/main-nextcloud-pdf.js
index 55d689c0f4a0e..339faa2da7d82 100644
--- a/apps/settings/src/main-nextcloud-pdf.js
+++ b/apps/settings/src/main-nextcloud-pdf.js
@@ -3,18 +3,31 @@
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
+import { getClient, getDefaultPropfind, getRootPath, resultToNode } from '@nextcloud/files/dav'
 import { loadState } from '@nextcloud/initial-state'
+import { getViewer } from '@nextcloud/viewer'
 
 const hasPdf = loadState('settings', 'has-reasons-use-nextcloud-pdf') === true
+const path = '/Reasons to use Nextcloud.pdf'
+
+/**
+ * Look the file up so the viewer can be handed a node.
+ */
+async function openInViewer() {
+	const { data } = await getClient().stat(getRootPath() + path, {
+		details: true,
+		data: getDefaultPropfind(),
+	})
+	const node = resultToNode(data)
+	await getViewer().open([node], node)
+}
 
 window.addEventListener('DOMContentLoaded', function() {
 	const link = document.getElementById('open-reasons-use-nextcloud-pdf')
 	if (link && hasPdf) {
 		link.addEventListener('click', function(event) {
 			event.preventDefault()
-			OCA.Viewer.open({
-				path: '/Reasons to use Nextcloud.pdf',
-			})
+			openInViewer()
 		})
 	}
 })
diff --git a/build/frontend/vite.config.ts b/build/frontend/vite.config.ts
index c292c3f371202..7cb4e616dbfda 100644
--- a/build/frontend/vite.config.ts
+++ b/build/frontend/vite.config.ts
@@ -10,6 +10,9 @@ const modules = {
 	appstore: {
 		main: resolve(import.meta.dirname, 'apps/appstore/src', 'main.ts'),
 	},
+	core: {
+		'viewer-init': resolve(import.meta.dirname, '../../core/src', 'viewer-init.ts'),
+	},
 	comments: {
 		'comments-app': resolve(import.meta.dirname, 'apps/comments/src', 'comments-app.ts'),
 		'comments-tab': resolve(import.meta.dirname, 'apps/comments/src', 'files-sidebar.ts'),
diff --git a/build/integration/features/provisioning-v1.feature b/build/integration/features/provisioning-v1.feature
index cb9006474ed32..2730581534e74 100644
--- a/build/integration/features/provisioning-v1.feature
+++ b/build/integration/features/provisioning-v1.feature
@@ -658,7 +658,6 @@ Feature: provisioning
       | updatenotification |
       | user_ldap |
       | user_status |
-      | viewer |
       | workflowengine |
       | webhook_listeners |
       | weather_status |
diff --git a/build/psalm-baseline.xml b/build/psalm-baseline.xml
index b9990096345cd..0b5ce194b598d 100644
--- a/build/psalm-baseline.xml
+++ b/build/psalm-baseline.xml
@@ -2349,11 +2349,6 @@
       <code><![CDATA[provideInitialState]]></code>
     </DeprecatedMethod>
   </file>
-  <file src="apps/settings/lib/Settings/Personal/ServerDevNotice.php">
-    <DeprecatedMethod>
-      <code><![CDATA[dispatch]]></code>
-    </DeprecatedMethod>
-  </file>
   <file src="apps/settings/lib/SetupChecks/CheckUserCertificates.php">
     <DeprecatedMethod>
       <code><![CDATA[getAppValue]]></code>
diff --git a/core/openapi-administration.json b/core/openapi-administration.json
index fdb5aa9e523cd..050a817249faf 100644
--- a/core/openapi-administration.json
+++ b/core/openapi-administration.json
@@ -33,7 +33,8 @@
                             "webdav-root",
                             "reference-api",
                             "reference-regex",
-                            "mod-rewrite-working"
+                            "mod-rewrite-working",
+                            "previews"
                         ],
                         "properties": {
                             "pollinterval": {
@@ -52,6 +53,20 @@
                             "mod-rewrite-working": {
                                 "type": "boolean"
                             },
+                            "previews": {
+                                "type": "object",
+                                "required": [
+                                    "enabled_providers"
+                                ],
+                                "properties": {
+                                    "enabled_providers": {
+                                        "type": "array",
+                                        "items": {
+                                            "type": "string"
+                                        }
+                                    }
+                                }
+                            },
                             "user": {
                                 "type": "object",
                                 "required": [
diff --git a/core/openapi-ex_app.json b/core/openapi-ex_app.json
index 17dbd07fe1ae5..fc5b382108dd7 100644
--- a/core/openapi-ex_app.json
+++ b/core/openapi-ex_app.json
@@ -33,7 +33,8 @@
                             "webdav-root",
                             "reference-api",
                             "reference-regex",
-                            "mod-rewrite-working"
+                            "mod-rewrite-working",
+                            "previews"
                         ],
                         "properties": {
                             "pollinterval": {
@@ -52,6 +53,20 @@
                             "mod-rewrite-working": {
                                 "type": "boolean"
                             },
+                            "previews": {
+                                "type": "object",
+                                "required": [
+                                    "enabled_providers"
+                                ],
+                                "properties": {
+                                    "enabled_providers": {
+                                        "type": "array",
+                                        "items": {
+                                            "type": "string"
+                                        }
+                                    }
+                                }
+                            },
                             "user": {
                                 "type": "object",
                                 "required": [
diff --git a/core/openapi-full.json b/core/openapi-full.json
index 9324c67bc87e9..2f4bc1c13af84 100644
--- a/core/openapi-full.json
+++ b/core/openapi-full.json
@@ -99,7 +99,8 @@
                             "webdav-root",
                             "reference-api",
                             "reference-regex",
-                            "mod-rewrite-working"
+                            "mod-rewrite-working",
+                            "previews"
                         ],
                         "properties": {
                             "pollinterval": {
@@ -118,6 +119,20 @@
                             "mod-rewrite-working": {
                                 "type": "boolean"
                             },
+                            "previews": {
+                                "type": "object",
+                                "required": [
+                                    "enabled_providers"
+                                ],
+                                "properties": {
+                                    "enabled_providers": {
+                                        "type": "array",
+                                        "items": {
+                                            "type": "string"
+                                        }
+                                    }
+                                }
+                            },
                             "user": {
                                 "type": "object",
                                 "required": [
diff --git a/core/openapi.json b/core/openapi.json
index d6d2915708009..b798a827b9bdb 100644
--- a/core/openapi.json
+++ b/core/openapi.json
@@ -99,7 +99,8 @@
                             "webdav-root",
                             "reference-api",
                             "reference-regex",
-                            "mod-rewrite-working"
+                            "mod-rewrite-working",
+                            "previews"
                         ],
                         "properties": {
                             "pollinterval": {
@@ -118,6 +119,20 @@
                             "mod-rewrite-working": {
                                 "type": "boolean"
                             },
+                            "previews": {
+                                "type": "object",
+                                "required": [
+                                    "enabled_providers"
+                                ],
+                                "properties": {
+                                    "enabled_providers": {
+                                        "type": "array",
+                                        "items": {
+                                            "type": "string"
+                                        }
+                                    }
+                                }
+                            },
                             "user": {
                                 "type": "object",
                                 "required": [
diff --git a/core/shipped.json b/core/shipped.json
index 81f734cfeb2cd..a068fa8f61569 100644
--- a/core/shipped.json
+++ b/core/shipped.json
@@ -53,7 +53,6 @@
     "updatenotification",
     "user_ldap",
     "user_status",
-    "viewer",
     "weather_status",
     "webhook_listeners",
     "workflowengine"
@@ -102,7 +101,6 @@
     "twofactor_totp",
     "updatenotification",
     "user_status",
-    "viewer",
     "weather_status",
     "webhook_listeners"
   ],
@@ -120,7 +118,6 @@
     "sharing",
     "theming",
     "twofactor_backupcodes",
-    "viewer",
     "workflowengine"
   ]
 }
diff --git a/core/src/viewer-init.ts b/core/src/viewer-init.ts
new file mode 100644
index 0000000000000..d22fb7acd2b09
--- /dev/null
+++ b/core/src/viewer-init.ts
@@ -0,0 +1,15 @@
+/*!
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { registerDefaultHandlers } from '@nextcloud/viewer'
+
+// Registers the handlers for images, video and audio, and offers this copy of
+// the viewer to the page. Nothing of the viewer itself is loaded until a file
+// is opened.
+//
+// This runs from an init script so those handlers, and the file actions they
+// register, are in place before the Files list takes its first snapshot of the
+// available actions.
+registerDefaultHandlers()
diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index fcfdd6ce50345..643b03dae144a 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -2401,6 +2401,7 @@
     'OC\\Template\\JSCombiner' => $baseDir . '/lib/private/Template/JSCombiner.php',
     'OC\\Template\\JSConfigHelper' => $baseDir . '/lib/private/Template/JSConfigHelper.php',
     'OC\\Template\\JSResourceLocator' => $baseDir . '/lib/private/Template/JSResourceLocator.php',
+    'OC\\Template\\LoadViewerListener' => $baseDir . '/lib/private/Template/LoadViewerListener.php',
     'OC\\Template\\ResourceLocator' => $baseDir . '/lib/private/Template/ResourceLocator.php',
     'OC\\Template\\ResourceNotFoundException' => $baseDir . '/lib/private/Template/ResourceNotFoundException.php',
     'OC\\Template\\Template' => $baseDir . '/lib/private/Template/Template.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index fa6bc202aa4e8..39fdc554a8b00 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -2442,6 +2442,7 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\Template\\JSCombiner' => __DIR__ . '/../../..' . '/lib/private/Template/JSCombiner.php',
         'OC\\Template\\JSConfigHelper' => __DIR__ . '/../../..' . '/lib/private/Template/JSConfigHelper.php',
         'OC\\Template\\JSResourceLocator' => __DIR__ . '/../../..' . '/lib/private/Template/JSResourceLocator.php',
+        'OC\\Template\\LoadViewerListener' => __DIR__ . '/../../..' . '/lib/private/Template/LoadViewerListener.php',
         'OC\\Template\\ResourceLocator' => __DIR__ . '/../../..' . '/lib/private/Template/ResourceLocator.php',
         'OC\\Template\\ResourceNotFoundException' => __DIR__ . '/../../..' . '/lib/private/Template/ResourceNotFoundException.php',
         'OC\\Template\\Template' => __DIR__ . '/../../..' . '/lib/private/Template/Template.php',
diff --git a/lib/private/OCS/CoreCapabilities.php b/lib/private/OCS/CoreCapabilities.php
index 2bab5d96677a5..bb4315ef4a3ec 100644
--- a/lib/private/OCS/CoreCapabilities.php
+++ b/lib/private/OCS/CoreCapabilities.php
@@ -12,6 +12,7 @@
 
 use OCP\Capabilities\ICapability;
 use OCP\IConfig;
+use OCP\IPreview;
 use OCP\IURLGenerator;
 
 /**
@@ -22,9 +23,11 @@
 class CoreCapabilities implements ICapability {
 	/**
 	 * @param IConfig $config
+	 * @param IPreview $preview
 	 */
 	public function __construct(
 		private IConfig $config,
+		private IPreview $preview,
 	) {
 	}
 
@@ -38,6 +41,9 @@ public function __construct(
 	 *         reference-api: boolean,
 	 *         reference-regex: string,
 	 *         mod-rewrite-working: boolean,
+	 *         previews: array{
+	 *             enabled_providers: list<string>,
+	 *         },
 	 *     },
 	 * }
 	 */
@@ -50,6 +56,13 @@ public function getCapabilities(): array {
 				'reference-api' => true,
 				'reference-regex' => IURLGenerator::URL_REGEX_NO_MODIFIERS,
 				'mod-rewrite-working' => $this->config->getSystemValueBool('htaccess.IgnoreFrontController') || getenv('front_controller_active') === 'true',
+				'previews' => [
+					// The mime patterns previews can be generated for. Empty
+					// when previews are off entirely. Clients use it to tell
+					// the formats a browser cannot show on its own but the
+					// server can render from the ones it can do neither of.
+					'enabled_providers' => array_keys($this->preview->getProviders()),
+				],
 			],
 		];
 	}
diff --git a/lib/private/Repair/CleanUpAbandonedApps.php b/lib/private/Repair/CleanUpAbandonedApps.php
index be08b210e5691..7eeac3e313008 100644
--- a/lib/private/Repair/CleanUpAbandonedApps.php
+++ b/lib/private/Repair/CleanUpAbandonedApps.php
@@ -13,7 +13,7 @@
 use OCP\Migration\IRepairStep;
 
 class CleanUpAbandonedApps implements IRepairStep {
-	protected const ABANDONED_APPS = ['accessibility', 'files_videoplayer'];
+	protected const ABANDONED_APPS = ['accessibility', 'files_videoplayer', 'viewer'];
 
 	public function __construct(
 		private readonly IConfig $config,
diff --git a/lib/private/Server.php b/lib/private/Server.php
index c1aae75d9fb48..dd6e56c54045b 100644
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@@ -149,6 +149,7 @@
 use OC\Talk\Broker;
 use OC\Teams\TeamManager;
 use OC\Template\JSCombiner;
+use OC\Template\LoadViewerListener;
 use OC\Translation\TranslationManager;
 use OC\User\AvailabilityCoordinator;
 use OC\User\DisplayNameCache;
@@ -163,6 +164,7 @@
 use OCP\Accounts\IAccountManager;
 use OCP\Activity\IEventMerger;
 use OCP\App\IAppManager;
+use OCP\AppFramework\Http\Events\BeforeTemplateRenderedEvent;
 use OCP\AppFramework\Utility\IControllerMethodReflector;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\Authentication\LoginCredentials\IStore;
@@ -906,7 +908,7 @@ public function __construct(
 		$this->registerService(CapabilitiesManager::class, function (ContainerInterface $c) {
 			$manager = new CapabilitiesManager($c->get(LoggerInterface::class));
 			$manager->registerCapability(function () use ($c) {
-				return new CoreCapabilities($c->get(IConfig::class));
+				return new CoreCapabilities($c->get(IConfig::class), $c->get(IPreview::class));
 			});
 			$manager->registerCapability(function () use ($c) {
 				return $c->get(Capabilities::class);
@@ -1189,6 +1191,7 @@ private function connectDispatcher(): void {
 		$eventDispatcher->addServiceListener(PostLoginEvent::class, UserLoggedInListener::class);
 		$eventDispatcher->addServiceListener(UserChangedEvent::class, UserChangedListener::class);
 		$eventDispatcher->addServiceListener(BeforeUserDeletedEvent::class, BeforeUserDeletedListener::class);
+		$eventDispatcher->addServiceListener(BeforeTemplateRenderedEvent::class, LoadViewerListener::class);
 
 		FilesMetadataManager::loadListeners($eventDispatcher);
 		GenerateBlurhashMetadata::loadListeners($eventDispatcher);
diff --git a/lib/private/Template/LoadViewerListener.php b/lib/private/Template/LoadViewerListener.php
new file mode 100644
index 0000000000000..981b477065877
--- /dev/null
+++ b/lib/private/Template/LoadViewerListener.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OC\Template;
+
+use OCP\AppFramework\Http\Events\BeforeTemplateRenderedEvent;
+use OCP\EventDispatcher\Event;
+use OCP\EventDispatcher\IEventListener;
+use OCP\Util;
+
+/**
+ * Put the viewer on every page a file can be opened from, which is any page an
+ * app can put a file link on rather than only the Files list. The script only
+ * registers the handlers; the viewer itself is fetched when a file is opened.
+ *
+ * @template-implements IEventListener<BeforeTemplateRenderedEvent>
+ */
+class LoadViewerListener implements IEventListener {
+	#[\Override]
+	public function handle(Event $event): void {
+		if (!($event instanceof BeforeTemplateRenderedEvent)) {
+			return;
+		}
+
+		Util::addInitScript('core', 'viewer-init');
+	}
+}
diff --git a/openapi.json b/openapi.json
index 1f862fa904b68..7827e05a45d31 100644
--- a/openapi.json
+++ b/openapi.json
@@ -149,7 +149,8 @@
                             "webdav-root",
                             "reference-api",
                             "reference-regex",
-                            "mod-rewrite-working"
+                            "mod-rewrite-working",
+                            "previews"
                         ],
                         "properties": {
                             "pollinterval": {
@@ -168,6 +169,20 @@
                             "mod-rewrite-working": {
                                 "type": "boolean"
                             },
+                            "previews": {
+                                "type": "object",
+                                "required": [
+                                    "enabled_providers"
+                                ],
+                                "properties": {
+                                    "enabled_providers": {
+                                        "type": "array",
+                                        "items": {
+                                            "type": "string"
+                                        }
+                                    }
+                                }
+                            },
                             "user": {
                                 "type": "object",
                                 "required": [
diff --git a/package-lock.json b/package-lock.json
index c62327a8617da..9b6a5c6505b3e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -26,6 +26,7 @@
         "@nextcloud/paths": "^3.1.0",
         "@nextcloud/router": "^3.1.0",
         "@nextcloud/sharing": "^1.0.0-beta.4",
+        "@nextcloud/viewer": "^2.0.0-beta.7",
         "@nextcloud/vue": "^9.10.0",
         "@vueuse/core": "^14.1.0",
         "@vueuse/integrations": "^14.1.0",
@@ -2020,6 +2021,24 @@
         "@nextcloud/files": "^3.12.0"
       }
     },
+    "node_modules/@nextcloud/image-editor": {
+      "version": "1.0.0-beta.2",
+      "resolved": "https://registry.npmjs.org/@nextcloud/image-editor/-/image-editor-1.0.0-beta.2.tgz",
+      "integrity": "sha512-WSyi/3DhGmtBAti9WLHBt5YKyQq1+tdBYdNe/DMkGHbOKV96C2bpNXp02TJg5LjH55P8NOVbuiXO4tndWJRTow==",
+      "license": "AGPL-3.0-or-later",
+      "dependencies": {
+        "@nextcloud/l10n": "^3.4.0",
+        "konva": "~10.3.2"
+      },
+      "engines": {
+        "node": "^20.0.0 || ^22.0.0 || ^24.0.0"
+      },
+      "peerDependencies": {
+        "@nextcloud/dialogs": "^7.0.0",
+        "@nextcloud/vue": "^9.0.0",
+        "vue": "^3.5.0"
+      }
+    },
     "node_modules/@nextcloud/initial-state": {
       "version": "3.0.0",
       "resolved": "https://registry.npmjs.org/@nextcloud/initial-state/-/initial-state-3.0.0.tgz",
@@ -2164,6 +2183,38 @@
         "node": "^20.0.0 || ^22.0.0 || ^24.0.0"
       }
     },
+    "node_modules/@nextcloud/viewer": {
+      "version": "2.0.0-beta.7",
+      "resolved": "https://registry.npmjs.org/@nextcloud/viewer/-/viewer-2.0.0-beta.7.tgz",
+      "integrity": "sha512-cCr3YDkILfN/Iwio1q9zycby+gt6D8oaJ193JIzMxGtuyWL4ewxztVRloU33KebZ/ixf4tIdqKI7MKudQDZoxg==",
+      "license": "AGPL-3.0-or-later",
+      "dependencies": {
+        "@mdi/svg": "^7.4.47",
+        "@nextcloud/image-editor": "^1.0.0-beta.2",
+        "@nextcloud/logger": "^3.0.3",
+        "@skjnldsv/vue-plyr": "^7.5.0",
+        "debounce": "^3.0.0",
+        "dompurify": "^3.4.14",
+        "vue-material-design-icons": "^5.3.1",
+        "webdav": "^5.10.0"
+      },
+      "engines": {
+        "node": "^20.0.0 || ^22.0.0 || ^24.0.0"
+      },
+      "peerDependencies": {
+        "@nextcloud/axios": "^2.5.2",
+        "@nextcloud/capabilities": "^1.2.1",
+        "@nextcloud/dialogs": "^7.5.0",
+        "@nextcloud/event-bus": "^3.3.3",
+        "@nextcloud/files": "^4.0.0",
+        "@nextcloud/l10n": "^3.4.1",
+        "@nextcloud/paths": "^3.1.0",
+        "@nextcloud/router": "^3.1.0",
+        "@nextcloud/sharing": "^0.4.0 || ^1.0.0-beta.2",
+        "@nextcloud/vue": "^9.10.0",
+        "vue": "^3.5.0"
+      }
+    },
     "node_modules/@nextcloud/vite-config": {
       "version": "2.5.4",
       "resolved": "https://registry.npmjs.org/@nextcloud/vite-config/-/vite-config-2.5.4.tgz",
@@ -3404,6 +3455,20 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/@skjnldsv/vue-plyr": {
+      "version": "7.5.0",
+      "resolved": "https://registry.npmjs.org/@skjnldsv/vue-plyr/-/vue-plyr-7.5.0.tgz",
+      "integrity": "sha512-JmbKPe8Eh0yTP+7w4VYeqGhrUqDKM4qSsCn37CbADAvvwMvceBwYC0IBXil0RBtyzStxwXPtOj1oI//lQ5DeTw==",
+      "license": "MIT",
+      "dependencies": {
+        "plyr": "^3.7.8",
+        "vue": "^3.3.4"
+      },
+      "engines": {
+        "node": "^18.0.0 || ^20.0.0",
+        "npm": "^9.0.0 || ^10.0.0"
+      }
+    },
     "node_modules/@standard-schema/spec": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/@standard-schema/spec/-/spec-1.1.0.tgz",
@@ -6436,6 +6501,12 @@
       "integrity": "sha512-z1HGKcYy2xA8AGQfwrn0PAy+PB7X/GSj3UVJW9qKyn43xWa+gl5nXmU4qqLMRzWVLFC8KusUX8T/0kCiOYpAIQ==",
       "license": "MIT"
     },
+    "node_modules/custom-event-polyfill": {
+      "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/custom-event-polyfill/-/custom-event-polyfill-1.0.7.tgz",
+      "integrity": "sha512-TDDkd5DkaZxZFM8p+1I3yAlvM3rSr1wbrOliG4yJiwinMZN8z/iGL7BTlDkrJcYTmgUSb4ywVCc3ZaUtOtC76w==",
+      "license": "MIT"
+    },
     "node_modules/data-uri-to-buffer": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/data-uri-to-buffer/-/data-uri-to-buffer-4.0.1.tgz",
@@ -9604,6 +9675,38 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/konva": {
+      "version": "10.3.3",
+      "resolved": "https://registry.npmjs.org/konva/-/konva-10.3.3.tgz",
+      "integrity": "sha512-j3Rrn504bYFwJ0zV0ZbSOQRsM9KMBLOpEq6xZuyIjbaKeFbBXwgiM5SA4IDq4nwM1l49GVKs66Mo+sl7+4G7PQ==",
+      "funding": [
+        {
+          "type": "patreon",
+          "url": "https://www.patreon.com/lavrton"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/konva"
+        },
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/lavrton"
+        }
+      ],
+      "license": "MIT",
+      "peerDependencies": {
+        "canvas": "^3.0.0",
+        "skia-canvas": "^3.0.0"
+      },
+      "peerDependenciesMeta": {
+        "canvas": {
+          "optional": true
+        },
+        "skia-canvas": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/layerr": {
       "version": "3.0.0",
       "resolved": "https://registry.npmjs.org/layerr/-/layerr-3.0.0.tgz",
@@ -9637,6 +9740,12 @@
       "integrity": "sha512-P8aEP5U/D1/IlTY2OeYsErdwh9bGuLE30NcXtKEjgdHcahveQoQwM2yZNsioQHsWFz0P7KKudisbrzCgR0sDHg==",
       "license": "MIT"
     },
+    "node_modules/loadjs": {
+      "version": "4.3.0",
+      "resolved": "https://registry.npmjs.org/loadjs/-/loadjs-4.3.0.tgz",
+      "integrity": "sha512-vNX4ZZLJBeDEOBvdr2v/F+0aN5oMuPu7JTqrMwp+DtgK+AryOlpy6Xtm2/HpNr+azEa828oQjOtWsB6iDtSfSQ==",
+      "license": "MIT"
+    },
     "node_modules/local-pkg": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/local-pkg/-/local-pkg-1.2.1.tgz",
@@ -11544,6 +11653,19 @@
         "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
       }
     },
+    "node_modules/plyr": {
+      "version": "3.8.4",
+      "resolved": "https://registry.npmjs.org/plyr/-/plyr-3.8.4.tgz",
+      "integrity": "sha512-DrzLbK9Wol3zeiuZCleD9aUOl0KAaBHR9H6WVVVYPZ4Ya+LYxUFTgSF1jooHcMQCv96Ws96wCaZzIoP3bES8pQ==",
+      "license": "MIT",
+      "dependencies": {
+        "core-js": "^3.45.1",
+        "custom-event-polyfill": "^1.0.7",
+        "loadjs": "^4.3.0",
+        "rangetouch": "^2.0.1",
+        "url-polyfill": "^1.1.13"
+      }
+    },
     "node_modules/possible-typed-array-names": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/possible-typed-array-names/-/possible-typed-array-names-1.1.0.tgz",
@@ -11957,6 +12079,12 @@
         "safe-buffer": "^5.1.0"
       }
     },
+    "node_modules/rangetouch": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/rangetouch/-/rangetouch-2.0.1.tgz",
+      "integrity": "sha512-sln+pNSc8NGaHoLzwNBssFSf/rSYkqeBXzX1AtJlkJiUaVSJSbRAWJk+4omsXkN+EJalzkZhWQ3th1m0FpR5xA==",
+      "license": "MIT"
+    },
     "node_modules/react-is": {
       "version": "17.0.2",
       "resolved": "https://registry.npmjs.org/react-is/-/react-is-17.0.2.tgz",
@@ -14476,6 +14604,12 @@
         "requires-port": "^1.0.0"
       }
     },
+    "node_modules/url-polyfill": {
+      "version": "1.1.14",
+      "resolved": "https://registry.npmjs.org/url-polyfill/-/url-polyfill-1.1.14.tgz",
+      "integrity": "sha512-p4f3TTAG6ADVF3mwbXw7hGw+QJyw5CnNGvYh5fCuQQZIiuKUswqcznyV3pGDP9j0TSmC4UvRKm8kl1QsX1diiQ==",
+      "license": "MIT"
+    },
     "node_modules/url/node_modules/punycode": {
       "version": "1.4.1",
       "resolved": "https://registry.npmjs.org/punycode/-/punycode-1.4.1.tgz",
diff --git a/package.json b/package.json
index dac70883a84f0..ade5c234132c0 100644
--- a/package.json
+++ b/package.json
@@ -55,6 +55,7 @@
     "@nextcloud/paths": "^3.1.0",
     "@nextcloud/router": "^3.1.0",
     "@nextcloud/sharing": "^1.0.0-beta.4",
+    "@nextcloud/viewer": "^2.0.0-beta.7",
     "@nextcloud/vue": "^9.10.0",
     "@vueuse/core": "^14.1.0",
     "@vueuse/integrations": "^14.1.0",
diff --git a/playwright.config.ts b/playwright.config.ts
index 4a7ccea10900b..47e9aa01f034b 100644
--- a/playwright.config.ts
+++ b/playwright.config.ts
@@ -14,6 +14,10 @@ const BROWSWER_CONFIG_CHROME: DeviceDescriptor & { channel: string } = {
 		: 'chromium', // locally use the default playwright chromium browser
 }
 
+// Port of the Nextcloud container under test. Override it to run several
+// checkouts in parallel, as each one needs its own server.
+const NEXTCLOUD_PORT = process.env.NEXTCLOUD_PORT ?? '8042'
+
 export default defineConfig({
 	testDir: './tests/playwright/e2e',
 	fullyParallel: true,
@@ -23,7 +27,7 @@ export default defineConfig({
 	timeout: process.env.CI ? 45_000 : undefined, // on CI allow 1.5x the default timeout to compensate for shared server resources
 	reporter: process.env.CI ? [['blob'], ['dot'], ['github']] : 'html',
 	use: {
-		baseURL: 'http://localhost:8042/index.php/',
+		baseURL: `http://localhost:${NEXTCLOUD_PORT}/index.php/`,
 		trace: 'on-first-retry',
 	},
 	projects: [
@@ -79,7 +83,7 @@ export default defineConfig({
 	webServer: {
 		command: 'node tests/playwright/start-nextcloud-server.js',
 		env: {
-			NEXTCLOUD_PORT: '8042',
+			NEXTCLOUD_PORT,
 		},
 		stderr: 'pipe',
 		stdout: 'pipe',
diff --git a/tests/data/REUSE.toml b/tests/data/REUSE.toml
index 3a19ce29f8384..2ace15bc9b815 100644
--- a/tests/data/REUSE.toml
+++ b/tests/data/REUSE.toml
@@ -122,3 +122,51 @@ path = "images/image.jpg"
 precedence = "aggregate"
 SPDX-FileCopyrightText = "2019 Tom Gainor <https://unsplash.com/@its_tgain> <https://unsplash.com/photos/mountain-cliff-under-starry-night-KidY3t8O4PE>"
 SPDX-License-Identifier = "LicenseRef-Unsplash"
+
+[[annotations]]
+path = ["media/image.gif", "media/image.ico", "media/image.svg", "media/image-small.png", "media/image-apng.png"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2019 Nextcloud GmbH"
+SPDX-License-Identifier = "LicenseRef-NextcloudTrademarks"
+
+[[annotations]]
+path = ["media/image1.jpg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2019 Stephen Leonardi <https://unsplash.com/@leo_visions_> <https://unsplash.com/photos/rock-formation-with-lava-during-daytime-eSNjFDbw_i4>"
+SPDX-License-Identifier = "LicenseRef-Unsplash"
+
+[[annotations]]
+path = ["media/image2.jpg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2019 Tom Gainor <https://unsplash.com/@its_tgain> <https://unsplash.com/photos/mountain-cliff-under-starry-night-KidY3t8O4PE>"
+SPDX-License-Identifier = "LicenseRef-Unsplash"
+
+[[annotations]]
+path = ["media/image4.jpg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2019 Vincent Riszdorfer <https://unsplash.com/@theguywithacamera> <https://unsplash.com/photos/person-about-to-claim-mountain-Q6X1ifPIfjs>"
+SPDX-License-Identifier = "LicenseRef-Unsplash"
+
+[[annotations]]
+path = ["media/video.mkv", "media/video.ogv", "media/video.webm", "media/video1.mp4"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2012 AnRo0002 <https://commons.wikimedia.org/wiki/User:AnRo0002>"
+SPDX-License-Identifier = "CC0-1.0"
+
+[[annotations]]
+path = ["media/audio.mp3", "media/audio.ogg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2022 AC Krah <https://commons.wikimedia.org/wiki/User:AC_Krah>"
+SPDX-License-Identifier = "CC0-1.0"
+
+[[annotations]]
+path = ["media/image3.jpg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2013 Wilfredor <https://commons.wikimedia.org/wiki/User:Wilfredor>"
+SPDX-License-Identifier = "CC0-1.0"
+
+[[annotations]]
+path = ["media/image.png", "media/image.webp"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2024 Master Unknown <https://unsplash.com/@exp00>"
+SPDX-License-Identifier = "LicenseRef-Unsplash"
diff --git a/tests/data/media/audio.mp3 b/tests/data/media/audio.mp3
new file mode 100644
index 0000000000000..d71cb7e4f56ee
Binary files /dev/null and b/tests/data/media/audio.mp3 differ
diff --git a/tests/data/media/audio.ogg b/tests/data/media/audio.ogg
new file mode 100644
index 0000000000000..661ba57eb726b
Binary files /dev/null and b/tests/data/media/audio.ogg differ
diff --git a/tests/data/media/image-apng.png b/tests/data/media/image-apng.png
new file mode 100644
index 0000000000000..73d2f6b962a3e
Binary files /dev/null and b/tests/data/media/image-apng.png differ
diff --git a/tests/data/media/image-small.png b/tests/data/media/image-small.png
new file mode 100644
index 0000000000000..a9128aa6afea5
Binary files /dev/null and b/tests/data/media/image-small.png differ
diff --git a/tests/data/media/image.gif b/tests/data/media/image.gif
new file mode 100644
index 0000000000000..4cb22be07b6e4
Binary files /dev/null and b/tests/data/media/image.gif differ
diff --git a/tests/data/media/image.ico b/tests/data/media/image.ico
new file mode 100644
index 0000000000000..b02c657782738
Binary files /dev/null and b/tests/data/media/image.ico differ
diff --git a/tests/data/media/image.png b/tests/data/media/image.png
new file mode 100644
index 0000000000000..205e6b3f70538
Binary files /dev/null and b/tests/data/media/image.png differ
diff --git a/tests/data/media/image.svg b/tests/data/media/image.svg
new file mode 100644
index 0000000000000..7008be01a195f
--- /dev/null
+++ b/tests/data/media/image.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 32 32" width="32" height="32"><rect rx="5" ry="5" height="32" width="32" fill="#0082c9"/><g transform="matrix(.12 0 0 .12 .64 8.32)" stroke="#fff" stroke-width="22" fill="none"><circle cy="64" cx="40" r="26"/><circle cy="64" cx="216" r="26"/><circle cy="64" cx="128" r="46"/></g></svg>
diff --git a/tests/data/media/image.webp b/tests/data/media/image.webp
new file mode 100644
index 0000000000000..8c9d8165c9cfe
Binary files /dev/null and b/tests/data/media/image.webp differ
diff --git a/tests/data/media/image1.jpg b/tests/data/media/image1.jpg
new file mode 100644
index 0000000000000..e561b9e1594b6
Binary files /dev/null and b/tests/data/media/image1.jpg differ
diff --git a/tests/data/media/image2.jpg b/tests/data/media/image2.jpg
new file mode 100644
index 0000000000000..46dac8cc2835c
Binary files /dev/null and b/tests/data/media/image2.jpg differ
diff --git a/tests/data/media/image3.jpg b/tests/data/media/image3.jpg
new file mode 100644
index 0000000000000..1feb689e477a6
Binary files /dev/null and b/tests/data/media/image3.jpg differ
diff --git a/tests/data/media/image4.jpg b/tests/data/media/image4.jpg
new file mode 100644
index 0000000000000..caf446d6c7e5d
Binary files /dev/null and b/tests/data/media/image4.jpg differ
diff --git a/tests/data/media/video.mkv b/tests/data/media/video.mkv
new file mode 100644
index 0000000000000..11d6323919995
Binary files /dev/null and b/tests/data/media/video.mkv differ
diff --git a/tests/data/media/video.ogv b/tests/data/media/video.ogv
new file mode 100644
index 0000000000000..d86f0ccba0056
Binary files /dev/null and b/tests/data/media/video.ogv differ
diff --git a/tests/data/media/video.webm b/tests/data/media/video.webm
new file mode 100644
index 0000000000000..244b522743c87
Binary files /dev/null and b/tests/data/media/video.webm differ
diff --git a/tests/data/media/video1.mp4 b/tests/data/media/video1.mp4
new file mode 100644
index 0000000000000..c94d7ab0715c7
Binary files /dev/null and b/tests/data/media/video1.mp4 differ
diff --git a/tests/lib/App/AppManagerTest.php b/tests/lib/App/AppManagerTest.php
index 26c5f9d60165c..9f6577cdb030f 100644
--- a/tests/lib/App/AppManagerTest.php
+++ b/tests/lib/App/AppManagerTest.php
@@ -564,7 +564,6 @@ public function testGetEnabledApps(): void {
 			'test3',
 			'theming',
 			'twofactor_backupcodes',
-			'viewer',
 			'workflowengine',
 		];
 		$this->assertEquals($apps, $this->manager->getEnabledApps());
@@ -597,7 +596,6 @@ public function testGetAppsForUser(): void {
 			'test3',
 			'theming',
 			'twofactor_backupcodes',
-			'viewer',
 			'workflowengine',
 		];
 		$this->assertEquals($enabled, $this->manager->getEnabledAppsForUser($user));
@@ -638,7 +636,6 @@ public function testGetAppsNeedingUpgrade(): void {
 			'sharing' => ['id' => 'sharing'],
 			'theming' => ['id' => 'theming'],
 			'twofactor_backupcodes' => ['id' => 'twofactor_backupcodes'],
-			'viewer' => ['id' => 'viewer'],
 			'workflowengine' => ['id' => 'workflowengine'],
 			'oauth2' => ['id' => 'oauth2'],
 		];
@@ -703,7 +700,6 @@ public function testGetIncompatibleApps(): void {
 			'twofactor_backupcodes' => ['id' => 'twofactor_backupcodes'],
 			'workflowengine' => ['id' => 'workflowengine'],
 			'oauth2' => ['id' => 'oauth2'],
-			'viewer' => ['id' => 'viewer'],
 		];
 
 		$manager->expects($this->any())
@@ -751,7 +747,6 @@ public function testGetEnabledAppsForGroup(): void {
 			'test3',
 			'theming',
 			'twofactor_backupcodes',
-			'viewer',
 			'workflowengine',
 		];
 		$this->assertEquals($enabled, $this->manager->getEnabledAppsForGroup($group));
diff --git a/tests/lib/AppTest.php b/tests/lib/AppTest.php
index 23cb10f0477e9..20349093c8c3e 100644
--- a/tests/lib/AppTest.php
+++ b/tests/lib/AppTest.php
@@ -109,7 +109,6 @@ public static function appConfigValuesProvider(): array {
 					'sharing',
 					'theming',
 					'twofactor_backupcodes',
-					'viewer',
 					'workflowengine',
 				],
 				false
@@ -135,7 +134,6 @@ public static function appConfigValuesProvider(): array {
 					'sharing',
 					'theming',
 					'twofactor_backupcodes',
-					'viewer',
 					'workflowengine',
 				],
 				false
@@ -162,7 +160,6 @@ public static function appConfigValuesProvider(): array {
 					'sharing',
 					'theming',
 					'twofactor_backupcodes',
-					'viewer',
 					'workflowengine',
 				],
 				false
@@ -189,7 +186,6 @@ public static function appConfigValuesProvider(): array {
 					'sharing',
 					'theming',
 					'twofactor_backupcodes',
-					'viewer',
 					'workflowengine',
 				],
 				false,
@@ -216,7 +212,6 @@ public static function appConfigValuesProvider(): array {
 					'sharing',
 					'theming',
 					'twofactor_backupcodes',
-					'viewer',
 					'workflowengine',
 				],
 				true,
@@ -279,11 +274,11 @@ public function testEnabledAppsCache(): void {
 			);
 
 		$apps = \OC_App::getEnabledApps();
-		$this->assertEquals(['files', 'app3', 'appstore', 'cloud_federation_api', 'dav', 'federatedfilesharing', 'lookup_server_connector', 'oauth2', 'profile', 'provisioning_api', 'settings', 'sharing', 'theming', 'twofactor_backupcodes', 'viewer', 'workflowengine'], $apps);
+		$this->assertEquals(['files', 'app3', 'appstore', 'cloud_federation_api', 'dav', 'federatedfilesharing', 'lookup_server_connector', 'oauth2', 'profile', 'provisioning_api', 'settings', 'sharing', 'theming', 'twofactor_backupcodes', 'workflowengine'], $apps);
 
 		// mock should not be called again here
 		$apps = \OC_App::getEnabledApps();
-		$this->assertEquals(['files', 'app3', 'appstore', 'cloud_federation_api', 'dav', 'federatedfilesharing', 'lookup_server_connector', 'oauth2', 'profile', 'provisioning_api', 'settings', 'sharing', 'theming', 'twofactor_backupcodes', 'viewer', 'workflowengine'], $apps);
+		$this->assertEquals(['files', 'app3', 'appstore', 'cloud_federation_api', 'dav', 'federatedfilesharing', 'lookup_server_connector', 'oauth2', 'profile', 'provisioning_api', 'settings', 'sharing', 'theming', 'twofactor_backupcodes', 'workflowengine'], $apps);
 
 		$this->restoreAppConfig();
 		$userSession->setUser(null);
diff --git a/tests/lib/OCS/CoreCapabilitiesTest.php b/tests/lib/OCS/CoreCapabilitiesTest.php
new file mode 100644
index 0000000000000..75ed32bc93438
--- /dev/null
+++ b/tests/lib/OCS/CoreCapabilitiesTest.php
@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\OCS;
+
+use OC\OCS\CoreCapabilities;
+use OCP\IConfig;
+use OCP\IPreview;
+use PHPUnit\Framework\MockObject\MockObject;
+use Test\TestCase;
+
+class CoreCapabilitiesTest extends TestCase {
+	private IConfig&MockObject $config;
+	private IPreview&MockObject $preview;
+	private CoreCapabilities $capabilities;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->config = $this->createMock(IConfig::class);
+		$this->preview = $this->createMock(IPreview::class);
+		$this->capabilities = new CoreCapabilities($this->config, $this->preview);
+	}
+
+	public function testEnabledPreviewProvidersAreReported(): void {
+		$this->preview->method('getProviders')
+			->willReturn([
+				'/image\/jpeg/' => [],
+				'/image\/hei(f|c)/' => [],
+			]);
+
+		$capabilities = $this->capabilities->getCapabilities();
+
+		$this->assertSame(
+			['/image\/jpeg/', '/image\/hei(f|c)/'],
+			$capabilities['core']['previews']['enabled_providers'],
+		);
+	}
+
+	public function testNoPreviewProvidersAreReportedWhenPreviewsAreOff(): void {
+		// The manager returns nothing at all when `enable_previews` is off
+		$this->preview->method('getProviders')->willReturn([]);
+
+		$capabilities = $this->capabilities->getCapabilities();
+
+		$this->assertSame([], $capabilities['core']['previews']['enabled_providers']);
+	}
+}
diff --git a/tests/playwright/e2e/viewer/a11y.spec.ts b/tests/playwright/e2e/viewer/a11y.spec.ts
new file mode 100644
index 0000000000000..e79691c3209f5
--- /dev/null
+++ b/tests/playwright/e2e/viewer/a11y.spec.ts
@@ -0,0 +1,31 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer accessibility', () => {
+	test.beforeEach(async ({ filesListPage, uploadMedia }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await uploadMedia('image2.jpg', 'image2.jpg', 'image/jpeg')
+		await uploadMedia('video1.mp4', 'video1.mp4', 'video/mp4')
+		await filesListPage.open()
+		await expect(filesListPage.getRowForFile('image1.jpg')).toBeVisible()
+	})
+
+	test('exposes the viewer as a labelled dialog with accessible controls', async ({ page, openFile, viewerPage }) => {
+		await openFile('image2.jpg')
+		await viewerPage.waitForOpen()
+
+		// The modal is a dialog labelled by the current file name.
+		const dialog = page.locator('.viewer__modal[role="dialog"]')
+		await expect(dialog).toBeVisible()
+		expect(await viewerPage.currentName()).toBe('image2.jpg')
+
+		// Navigation and close controls have accessible names.
+		await expect(viewerPage.nextButton).toBeVisible()
+		await expect(viewerPage.previousButton).toBeVisible()
+		await expect(viewerPage.closeButton).toBeVisible()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/close.spec.ts b/tests/playwright/e2e/viewer/actions/close.spec.ts
new file mode 100644
index 0000000000000..cd903ac58d5a5
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/close.spec.ts
@@ -0,0 +1,23 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { test } from '../../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer close on click outside', () => {
+	test.beforeEach(async ({ filesListPage, uploadMedia }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await filesListPage.open()
+	})
+
+	// Regression for nextcloud/viewer#2166: clicking outside the image closes it.
+	test('closes when clicking outside the media', async ({ openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		await viewerPage.clickOutside()
+
+		await viewerPage.waitForClosed()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/delete.spec.ts b/tests/playwright/e2e/viewer/actions/delete.spec.ts
new file mode 100644
index 0000000000000..b5a8fc63991cd
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/delete.spec.ts
@@ -0,0 +1,29 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer delete action', () => {
+	// Deleting the shown file advances the viewer to the next file, then the
+	// previous one, then closes when nothing is left.
+	test('advances to the next file, then closes when the list is empty', async ({ filesListPage, uploadMedia, openFile, viewerPage }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await uploadMedia('image2.jpg', 'image2.jpg', 'image/jpeg')
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		// Delete the first file → viewer moves to the second, staying open.
+		await viewerPage.runAction('Delete file')
+		await viewerPage.waitForOpen()
+		await expect(async () => {
+			expect(await viewerPage.currentName()).toBe('image2.jpg')
+		}).toPass()
+
+		// Delete the only remaining file → viewer closes.
+		await viewerPage.runAction('Delete file')
+		await viewerPage.waitForClosed()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/download.spec.ts b/tests/playwright/e2e/viewer/actions/download.spec.ts
new file mode 100644
index 0000000000000..e5e4ab487d0de
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/download.spec.ts
@@ -0,0 +1,31 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, sharingTest as test, uploadMediaFile } from '../../../support/fixtures/viewer-page.ts'
+import { mkdir } from '../../../support/utils/dav.ts'
+import { createShare, DOWNLOAD_DISABLED_ATTRIBUTE, waitForShare } from '../../../support/utils/sharing.ts'
+
+test.describe('Viewer download restrictions', () => {
+	// The owner shares a folder with the current user, forbidding download. The
+	// recipient must then get no download control in the viewer.
+	test('does not expose a download control when download is forbidden', async ({ page, user, owner, ownerRequest, filesListPage, viewerPage }) => {
+		await mkdir(ownerRequest, owner, '/Photos')
+		await uploadMediaFile(ownerRequest, owner, 'image1.jpg', '/Photos/image1.jpg', 'image/jpeg')
+		await createShare(ownerRequest, '/Photos', user.userId, { attributes: DOWNLOAD_DISABLED_ATTRIBUTE })
+		await waitForShare(page.request, user, '', 'Photos')
+
+		await filesListPage.open()
+		await filesListPage.getRowNameLinkForFile('Photos').click()
+		await expect(filesListPage.getRowForFile('image1.jpg')).toBeVisible()
+
+		await filesListPage.getRowNameLinkForFile('image1.jpg').click()
+		await viewerPage.isVisible()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+
+		// No download link nor download action is offered in the viewer.
+		await expect(viewerPage.modal.locator('a[download]')).toHaveCount(0)
+		await expect(viewerPage.modal.getByRole('button', { name: /download/i })).toHaveCount(0)
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/edit.spec.ts b/tests/playwright/e2e/viewer/actions/edit.spec.ts
new file mode 100644
index 0000000000000..5f955c70af2cb
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/edit.spec.ts
@@ -0,0 +1,54 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer image editor action', () => {
+	test.beforeEach(async ({ filesListPage, uploadMedia }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await filesListPage.open()
+		await expect(filesListPage.getRowForFile('image1.jpg')).toBeVisible()
+	})
+
+	// The Edit action opens @nextcloud/image-editor; its Cancel closes it.
+	test('opens the image editor and closes it on cancel', async ({ page, openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		await viewerPage.runAction('Edit')
+		const editor = page.locator('.viewer__image-editor.image-editor')
+		await expect(editor).toBeVisible()
+		expect(page.url()).toContain('editing=true')
+
+		await page.locator('[data-test="cancel"], [data-test="cancel-icon"]').first().click()
+		await expect(editor).toBeHidden()
+		expect(page.url()).not.toContain('editing=true')
+	})
+
+	// Saving overwrites the file and shows the edited image from its local blob,
+	// without a server refetch.
+	test('saves and shows the edited image without a refetch', async ({ page, openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		await viewerPage.runAction('Edit')
+		await expect(page.locator('.viewer__image-editor.image-editor')).toBeVisible()
+
+		await page.locator('[data-test="save"]').click()
+
+		await expect(page.locator('.viewer__image-editor.image-editor')).toBeHidden()
+		await expect(page.locator('oca-viewer-image img')).toHaveAttribute('src', /^blob:/)
+	})
+
+	// The `editing=true` URL param reopens the editor on refresh.
+	test('reopens the editor from an editing=true URL', async ({ page, openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		await viewerPage.runAction('Edit')
+		await expect(page.locator('.viewer__image-editor.image-editor')).toBeVisible()
+
+		await page.reload()
+		await expect(page.locator('.viewer__image-editor.image-editor')).toBeVisible()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/menu.spec.ts b/tests/playwright/e2e/viewer/actions/menu.spec.ts
new file mode 100644
index 0000000000000..198fa58c62efb
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/menu.spec.ts
@@ -0,0 +1,34 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer actions menu', () => {
+	// The viewer links its header menu to the Files actions. Actions rendered by
+	// a custom component (e.g. the sharing status) have no static label/icon and
+	// must be filtered out, otherwise they show up as blank menu entries.
+	test('does not render blank entries for custom-rendered file actions', async ({ page, filesListPage, uploadMedia, openFile, viewerPage }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		const toggle = viewerPage.actionsToggle()
+		await toggle.click()
+
+		const menuItems = page.getByRole('menuitem')
+		await expect(menuItems.first()).toBeVisible()
+
+		// Every menu entry must have a non-empty accessible label.
+		const labels = await menuItems.allInnerTexts()
+		expect(labels.length).toBeGreaterThan(0)
+		for (const label of labels) {
+			expect(label.trim()).not.toBe('')
+		}
+
+		// The sharing-status action is custom-rendered and must be absent.
+		await expect(page.getByRole('menuitem', { name: /sharing/i })).toHaveCount(0)
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/rename.spec.ts b/tests/playwright/e2e/viewer/actions/rename.spec.ts
new file mode 100644
index 0000000000000..751769294c721
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/rename.spec.ts
@@ -0,0 +1,31 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer rename action', () => {
+	// The Files rename action edits the file-list row, which the viewer cannot
+	// host, so the viewer renames through its own dialog instead.
+	test('renames the current file from the viewer', async ({ page, filesListPage, uploadMedia, openFile, viewerPage }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		await viewerPage.runAction('Rename')
+
+		const dialog = page.getByRole('dialog', { name: 'Rename file' })
+		await expect(dialog).toBeVisible()
+		const input = dialog.getByRole('textbox')
+		await input.fill('renamed.jpg')
+		await dialog.getByRole('button', { name: 'Rename' }).click()
+
+		await expect(dialog).toBeHidden()
+		// The header reflects the new name.
+		await expect(async () => {
+			expect(await viewerPage.currentName()).toBe('renamed.jpg')
+		}).toPass()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/actions/sidebar.spec.ts b/tests/playwright/e2e/viewer/actions/sidebar.spec.ts
new file mode 100644
index 0000000000000..f2431c0232e41
--- /dev/null
+++ b/tests/playwright/e2e/viewer/actions/sidebar.spec.ts
@@ -0,0 +1,79 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer sidebar action', () => {
+	test.beforeEach(async ({ filesListPage, uploadMedia }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await filesListPage.open()
+		await expect(filesListPage.getRowForFile('image1.jpg')).toBeVisible()
+	})
+
+	test('opens the Files sidebar for the current file', async ({ page, openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		await viewerPage.openSidebar()
+
+		const sidebar = page.locator('aside.app-sidebar')
+		await expect(sidebar).toBeVisible()
+		await expect(sidebar.locator('.app-sidebar-header__mainname')).toContainText('image1.jpg')
+	})
+
+	// The sidebar next to the viewer must fill the full height (the app header is
+	// hidden), like the pre-7.0.0 viewer did.
+	test('shows the sidebar full height next to the viewer', async ({ page, openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		await viewerPage.openSidebar()
+
+		const sidebar = page.locator('aside.app-sidebar')
+		await expect(sidebar).toBeVisible()
+
+		await expect(async () => {
+			const full = await page.evaluate(() => {
+				const el = document.querySelector('aside.app-sidebar')!
+				const header = document.querySelector('#header')
+				return document.body.classList.contains('viewer--sidebar-fullscreen')
+					&& getComputedStyle(el).position === 'fixed'
+					&& (!header || getComputedStyle(header).visibility === 'hidden')
+					&& Math.round(el.getBoundingClientRect().height) === window.innerHeight
+			})
+			expect(full).toBe(true)
+		}).toPass()
+	})
+
+	// Regression for nextcloud/viewer#658: opening the sidebar while the image is
+	// still loading must still show the sidebar (the header actions are available
+	// during loading).
+	test('opens the sidebar while the image is still loading', async ({ page, openFile, viewerPage }) => {
+		// The previews of the file list are held back as well, so the whole test
+		// runs against delayed responses and needs more than the default budget.
+		test.slow()
+
+		// Hold the preview response so the viewer stays in its loading state long
+		// enough to interact with the header while loading.
+		await page.route('**/core/preview*', async (route) => {
+			await new Promise((resolve) => setTimeout(resolve, 3000))
+			await route.continue()
+		})
+
+		await openFile('image1.jpg')
+		await expect(viewerPage.container).toBeVisible()
+		await expect(viewerPage.loading).toHaveCount(1)
+
+		await viewerPage.openSidebar()
+
+		const sidebar = page.locator('aside.app-sidebar')
+		await expect(sidebar).toBeVisible()
+
+		// The image still finishes loading afterwards. Stop holding the previews
+		// back first: opening the sidebar resizes the viewer, which requests the
+		// preview again, and that request would be delayed as well.
+		await page.unroute('**/core/preview*')
+		await viewerPage.waitForOpen()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/audios.spec.ts b/tests/playwright/e2e/viewer/audios.spec.ts
new file mode 100644
index 0000000000000..9f6980f150e2e
--- /dev/null
+++ b/tests/playwright/e2e/viewer/audios.spec.ts
@@ -0,0 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { AUDIO_MEDIA, createMediaViewerTests } from './media.ts'
+
+createMediaViewerTests(AUDIO_MEDIA)
diff --git a/tests/playwright/e2e/viewer/compare.spec.ts b/tests/playwright/e2e/viewer/compare.spec.ts
new file mode 100644
index 0000000000000..f820caab609e7
--- /dev/null
+++ b/tests/playwright/e2e/viewer/compare.spec.ts
@@ -0,0 +1,53 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer compare API', () => {
+	// The compare() API renders two files side by side. It has no Files-app UI
+	// (it is used programmatically, e.g. by files_versions), so we capture two
+	// real File nodes by opening them, then call the public viewer service.
+	test('renders two files side by side', async ({ page, filesListPage, uploadMedia, openFile, viewerPage }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await uploadMedia('image2.jpg', 'image2.jpg', 'image/jpeg')
+		await filesListPage.open()
+
+		// Capture the File node passed to the viewer for each opened file.
+		await page.evaluate(() => {
+			const win = window as unknown as {
+				__capturedNodes: unknown[]
+				_nc_viewer_scope: Record<string, { service: { open: (...args: unknown[]) => unknown } }>
+			}
+			win.__capturedNodes = []
+			const service = win._nc_viewer_scope.handlers_v1!.service
+			const original = service.open.bind(service)
+			service.open = (nodes: unknown, file: unknown, ...rest: unknown[]) => {
+				win.__capturedNodes.push(file)
+				return original(nodes, file, ...rest)
+			}
+		})
+
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		await viewerPage.close()
+
+		await openFile('image2.jpg')
+		await viewerPage.waitForOpen()
+		await viewerPage.close()
+
+		// Programmatically compare the two captured nodes.
+		await page.evaluate(async () => {
+			const win = window as unknown as {
+				__capturedNodes: unknown[]
+				_nc_viewer_scope: Record<string, { service: { compare: (a: unknown, b: unknown) => Promise<void> } }>
+			}
+			await win._nc_viewer_scope.handlers_v1!.service.compare(win.__capturedNodes[0], win.__capturedNodes[1])
+		})
+
+		const comparison = viewerPage.modal.locator('.viewer__comparison')
+		await expect(comparison).toBeVisible()
+		await expect(comparison.locator('oca-viewer-image')).toHaveCount(2)
+	})
+})
diff --git a/tests/playwright/e2e/viewer/error.spec.ts b/tests/playwright/e2e/viewer/error.spec.ts
new file mode 100644
index 0000000000000..46343d7f38ea6
--- /dev/null
+++ b/tests/playwright/e2e/viewer/error.spec.ts
@@ -0,0 +1,24 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { test } from '../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer error handling', () => {
+	// A media file that fails to load must show an error, not stay stuck on the
+	// loading spinner (regression guard for the loading-gate / onError path).
+	test('shows an error when the media fails to load', async ({ page, filesListPage, uploadMedia, openFile, viewerPage }) => {
+		await uploadMedia('video1.mp4', 'video1.mp4', 'video/mp4')
+
+		// Make every request for the video fail: the direct source and the E2EE
+		// fallback fetch both hit the dav endpoint for this file.
+		await page.route('**/video1.mp4', (route) => route.abort())
+		await page.route('**/video1.mp4?**', (route) => route.abort())
+
+		await filesListPage.open()
+		await openFile('video1.mp4')
+
+		await viewerPage.expectError()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/history.spec.ts b/tests/playwright/e2e/viewer/history.spec.ts
new file mode 100644
index 0000000000000..8a94c409aba89
--- /dev/null
+++ b/tests/playwright/e2e/viewer/history.spec.ts
@@ -0,0 +1,76 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+test.describe('Viewer browser history', () => {
+	test.beforeEach(async ({ uploadMedia }) => {
+		await uploadMedia('image1.jpg', 'image1.jpg', 'image/jpeg')
+		await uploadMedia('image2.jpg', 'image2.jpg', 'image/jpeg')
+	})
+
+	test('reflects the open file in the URL and re-opens on refresh', async ({ page, filesListPage, openFile, viewerPage }) => {
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		// Opening pushes an openfile URL so a refresh re-triggers the viewer.
+		expect(page.url()).toContain('openfile=true')
+
+		await page.reload()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+	})
+
+	test('back and forward move between the shown files', async ({ page, filesListPage, openFile, viewerPage }) => {
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		const openUrl = page.url()
+
+		await viewerPage.next()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image2.jpg')
+		// Navigating pushed a new history entry.
+		expect(page.url()).not.toBe(openUrl)
+
+		// Browser back returns to the first file, still inside the viewer.
+		await page.goBack()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+
+		// Browser forward returns to the second file.
+		await page.goForward()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image2.jpg')
+	})
+
+	test('closing resets history so back does not re-open a file', async ({ page, filesListPage, openFile, viewerPage }) => {
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		await viewerPage.next()
+		await viewerPage.waitForOpen()
+
+		await viewerPage.close()
+		// The openfile flag is gone from the URL…
+		expect(page.url()).not.toContain('openfile=true')
+
+		// …and pressing back does not step back into the images.
+		await page.goBack()
+		await viewerPage.waitForClosed()
+	})
+
+	test('navigating out of the openfile range closes the viewer', async ({ page, filesListPage, openFile, viewerPage }) => {
+		await filesListPage.open()
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+
+		// A single back from the first file leaves the openfile range → close.
+		await page.goBack()
+		await viewerPage.waitForClosed()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/images.spec.ts b/tests/playwright/e2e/viewer/images.spec.ts
new file mode 100644
index 0000000000000..1e52424d7bb7c
--- /dev/null
+++ b/tests/playwright/e2e/viewer/images.spec.ts
@@ -0,0 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { createMediaViewerTests, IMAGE_MEDIA } from './media.ts'
+
+createMediaViewerTests(IMAGE_MEDIA)
diff --git a/tests/playwright/e2e/viewer/large-folder.spec.ts b/tests/playwright/e2e/viewer/large-folder.spec.ts
new file mode 100644
index 0000000000000..a637e0469d90b
--- /dev/null
+++ b/tests/playwright/e2e/viewer/large-folder.spec.ts
@@ -0,0 +1,33 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+// Zero-padded so the natural file-list order matches the numeric order.
+const COUNT = 30
+const name = (index: number): string => `image-${String(index).padStart(3, '0')}.jpg`
+
+test.describe('Viewer in a large folder', () => {
+	// Regression for nextcloud/viewer#3015: opening a file in a directory with
+	// many files used to hang (O(n^2) sort). The viewer now trusts the caller's
+	// order, so opening and navigating stays responsive.
+	test('opens quickly and navigates in a folder with many files', async ({ filesListPage, uploadMedia, openFile, viewerPage }) => {
+		await Promise.all(Array.from({ length: COUNT }, (_, index) => uploadMedia('image1.jpg', name(index), 'image/jpeg')))
+		await filesListPage.open()
+		await expect(filesListPage.getRowForFile(name(0))).toBeVisible()
+
+		const start = Date.now()
+		await openFile(name(0))
+		await viewerPage.waitForOpen()
+		// The prev/next controls become available well within a sane budget.
+		expect(Date.now() - start).toBeLessThan(15000)
+
+		expect(await viewerPage.currentName()).toBe(name(0))
+
+		await viewerPage.next()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe(name(1))
+	})
+})
diff --git a/tests/playwright/e2e/viewer/media.ts b/tests/playwright/e2e/viewer/media.ts
new file mode 100644
index 0000000000000..8e410ca53c3ad
--- /dev/null
+++ b/tests/playwright/e2e/viewer/media.ts
@@ -0,0 +1,88 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { MediaKind } from '../../support/sections/ViewerPage.ts'
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+export interface MediaItem {
+	/** Fixture file name in `tests/data/media`. */
+	fixture: string
+	/** Content type used when uploading the fixture. */
+	mime: string
+	/** Media kind handled by the viewer. */
+	kind: MediaKind
+	/** The handler custom element tag name. */
+	handlerTag: string
+	/**
+	 * If set, the standard tests are skipped with this reason.
+	 * Used for codecs unsupported by Playwright's bundled Chromium.
+	 */
+	skip?: string
+}
+
+/** Images ported from the Cypress image specs and the image mixin. */
+export const IMAGE_MEDIA: MediaItem[] = [
+	{ fixture: 'image1.jpg', mime: 'image/jpeg', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image.png', mime: 'image/png', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image.gif', mime: 'image/gif', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image.webp', mime: 'image/webp', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image.svg', mime: 'image/svg+xml', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image.ico', mime: 'image/x-icon', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image-apng.png', mime: 'image/png', kind: 'image', handlerTag: 'oca-viewer-image' },
+	{ fixture: 'image-small.png', mime: 'image/png', kind: 'image', handlerTag: 'oca-viewer-image' },
+]
+
+/** Videos ported from the Cypress video specs and the video mixin. */
+export const VIDEO_MEDIA: MediaItem[] = [
+	{ fixture: 'video1.mp4', mime: 'video/mp4', kind: 'video', handlerTag: 'oca-viewer-video' },
+	{ fixture: 'video.webm', mime: 'video/webm', kind: 'video', handlerTag: 'oca-viewer-video' },
+	{ fixture: 'video.mkv', mime: 'video/x-matroska', kind: 'video', handlerTag: 'oca-viewer-video' },
+	{
+		fixture: 'video.ogv',
+		mime: 'video/ogg',
+		kind: 'video',
+		handlerTag: 'oca-viewer-video',
+		// Ogg/Theora is not supported by Playwright's bundled Chromium.
+		skip: 'Ogg/Theora codec is unsupported by Playwright bundled Chromium',
+	},
+]
+
+/** Audios ported from the Cypress audio specs and the audio mixin. */
+export const AUDIO_MEDIA: MediaItem[] = [
+	{ fixture: 'audio.mp3', mime: 'audio/mpeg', kind: 'audio', handlerTag: 'oca-viewer-audio' },
+	{ fixture: 'audio.ogg', mime: 'audio/ogg', kind: 'audio', handlerTag: 'oca-viewer-audio' },
+]
+
+/**
+ * Register the standard open → load → assert → close test for a media item.
+ *
+ * This is the Playwright port of the Cypress `image`, `video` and `audio`
+ * mixins: it uploads a single fixture, opens it from the files list, waits for
+ * the viewer to finish loading, asserts the correct handler is rendered and
+ * that a single file shows no navigation arrows, then closes the viewer.
+ *
+ * @param media - The media items to generate tests for
+ */
+export function createMediaViewerTests(media: MediaItem[]): void {
+	for (const item of media) {
+		test(`opens ${item.fixture} in the viewer`, async ({ filesListPage, viewerPage, uploadMedia, openFile }) => {
+			test.skip(Boolean(item.skip), item.skip ?? '')
+
+			await uploadMedia(item.fixture, item.fixture, item.mime)
+			await filesListPage.open()
+
+			await expect(filesListPage.getRowForFile(item.fixture)).toBeVisible()
+
+			await openFile(item.fixture)
+			await viewerPage.waitForOpen()
+
+			expect(await viewerPage.currentName()).toBe(item.fixture)
+			await viewerPage.expectHandler(item.kind)
+
+			await viewerPage.close()
+		})
+	}
+}
diff --git a/tests/playwright/e2e/viewer/navigation.spec.ts b/tests/playwright/e2e/viewer/navigation.spec.ts
new file mode 100644
index 0000000000000..3bc7f967ff51c
--- /dev/null
+++ b/tests/playwright/e2e/viewer/navigation.spec.ts
@@ -0,0 +1,58 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+const IMAGES = ['image1.jpg', 'image2.jpg', 'image3.jpg', 'image4.jpg']
+
+test.describe('Viewer navigation', () => {
+	test.beforeEach(async ({ filesListPage, uploadMedia }) => {
+		for (const image of IMAGES) {
+			await uploadMedia(image, image, 'image/jpeg')
+		}
+		await filesListPage.open()
+		await expect(filesListPage.getRowForFile('image1.jpg')).toBeVisible()
+	})
+
+	test('navigates forward through the list and loops back to the first image', async ({ openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+
+		// The list has several images: navigation arrows are shown.
+		await expect(viewerPage.nextButton).toBeVisible()
+		await expect(viewerPage.previousButton).toBeVisible()
+
+		for (const image of ['image2.jpg', 'image3.jpg', 'image4.jpg']) {
+			await viewerPage.next()
+			await viewerPage.waitForOpen()
+			expect(await viewerPage.currentName()).toBe(image)
+			await viewerPage.expectHandler('image')
+		}
+
+		// Looping from the last image back to the first.
+		await viewerPage.next()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+	})
+
+	test('navigates backward and loops from the first image to the last', async ({ openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+
+		await viewerPage.previous()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image4.jpg')
+	})
+
+	test('closes the viewer when navigating back in the browser', async ({ page, openFile, viewerPage }) => {
+		await openFile('image1.jpg')
+		await viewerPage.isVisible()
+
+		await page.goBack()
+		await expect(viewerPage.container).toBeHidden()
+	})
+})
diff --git a/tests/playwright/e2e/viewer/oddname.spec.ts b/tests/playwright/e2e/viewer/oddname.spec.ts
new file mode 100644
index 0000000000000..bd49c543a9c94
--- /dev/null
+++ b/tests/playwright/e2e/viewer/oddname.spec.ts
@@ -0,0 +1,138 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { MediaKind } from '../../support/sections/ViewerPage.ts'
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+import { FilesListPage } from '../../support/sections/FilesListPage.ts'
+import { ViewerPage } from '../../support/sections/ViewerPage.ts'
+import { mkdir } from '../../support/utils/dav.ts'
+import { createLinkShare } from '../../support/utils/sharing.ts'
+
+/**
+ * Build a name aimed at breaking the viewer in case of escaping errors.
+ *
+ * @param realName - The original file name
+ */
+function naughtyFileName(realName: string): string {
+	const ext = realName.split('.').pop() ?? ''
+	return (
+		'~⛰️ shot of a $[big} mountain`, '
+		+ "realy #1's "
+		+ '" #_+="%2520%27%22%60%25%21%23 was this called '
+		+ realName
+		+ 'in the'
+		+ '☁️'
+		+ '👩‍💻'
+		+ '? :* .'
+		+ ext.toUpperCase()
+	)
+}
+
+/**
+ * Build a folder name with special characters around a file name.
+ *
+ * @param realName - The original file name
+ */
+function naughtyFolderName(realName: string): string {
+	return 'Nextcloud "%27%22%60%25%21%23" >`⛰️<' + realName + "><` e*'rocks!#?#%~"
+}
+
+interface OddCase {
+	fixture: string
+	mime: string
+	kind: MediaKind
+}
+
+const CASES: OddCase[] = [
+	{ fixture: 'image.png', mime: 'image/png', kind: 'image' },
+	{ fixture: 'video1.mp4', mime: 'video/mp4', kind: 'video' },
+	{ fixture: 'audio.mp3', mime: 'audio/mpeg', kind: 'audio' },
+]
+
+for (const testCase of CASES) {
+	const placedName = naughtyFileName(testCase.fixture)
+	const folderName = naughtyFolderName(testCase.fixture)
+
+	test.describe(`Odd file name (${testCase.fixture})`, () => {
+		test.beforeEach(async ({ page, user, filesListPage, uploadMedia }) => {
+			await mkdir(page.request, user, `/${folderName}`)
+			await uploadMedia(testCase.fixture, `/${folderName}/${placedName}`, testCase.mime)
+			await filesListPage.open()
+		})
+
+		test('opens a file with an odd name in the viewer', async ({ filesListPage, openFile, viewerPage }) => {
+			await openFile(folderName)
+			await expect(filesListPage.getRowForFile(placedName)).toBeVisible()
+
+			await openFile(placedName)
+			await viewerPage.waitForOpen()
+
+			expect(await viewerPage.currentName()).toBe(placedName)
+			await viewerPage.expectHandler(testCase.kind)
+
+			await viewerPage.close()
+		})
+	})
+}
+
+test.describe('Odd file name (image, sidebar and public share)', () => {
+	const fixture = 'image.png'
+	const placedName = naughtyFileName(fixture)
+	const folderName = naughtyFolderName(fixture)
+
+	test.beforeEach(async ({ page, user, filesListPage, uploadMedia }) => {
+		await mkdir(page.request, user, `/${folderName}`)
+		await uploadMedia(fixture, `/${folderName}/${placedName}`, 'image/png')
+		await filesListPage.open()
+	})
+
+	test('opens the sidebar for an odd file name', async ({ page, openFile, viewerPage }) => {
+		await openFile(folderName)
+		await openFile(placedName)
+		await viewerPage.waitForOpen()
+
+		await viewerPage.openSidebar()
+
+		const sidebar = page.locator('aside.app-sidebar')
+		await expect(sidebar).toBeVisible()
+		await expect(sidebar.locator('.app-sidebar-header__mainname')).toContainText(placedName)
+	})
+
+	test('opens an odd file name from a public link share', async ({ browser, baseURL, playwright, user }) => {
+		// Seed and share as the owner through a clean basic-auth request context —
+		// browser session cookies would otherwise win over basic auth.
+		const ownerRequest = await playwright.request.newContext({
+			baseURL,
+			httpCredentials: { username: user.userId, password: user.password, send: 'always' },
+		})
+		let share
+		try {
+			share = await createLinkShare(ownerRequest, `/${folderName}`)
+		} finally {
+			await ownerRequest.dispose()
+		}
+
+		// Visit the share as an anonymous guest, in a fresh unauthenticated context.
+		const context = await browser.newContext({ storageState: undefined, baseURL })
+		try {
+			const guestPage = await context.newPage()
+			await guestPage.goto(share.url)
+
+			const filesListPage = new FilesListPage(guestPage)
+			const viewerPage = new ViewerPage(guestPage)
+
+			await expect(filesListPage.getRowForFile(placedName)).toBeVisible()
+
+			await filesListPage.getRowNameLinkForFile(placedName).click()
+			await viewerPage.waitForOpen()
+
+			expect(await viewerPage.currentName()).toBe(placedName)
+			await viewerPage.expectHandler('image')
+		} finally {
+			await context.close()
+		}
+	})
+})
diff --git a/tests/playwright/e2e/viewer/sharing.spec.ts b/tests/playwright/e2e/viewer/sharing.spec.ts
new file mode 100644
index 0000000000000..8fd9edf08f4d8
--- /dev/null
+++ b/tests/playwright/e2e/viewer/sharing.spec.ts
@@ -0,0 +1,63 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, publicShareTest as test, uploadMediaFile } from '../../support/fixtures/viewer-page.ts'
+import { mkdir } from '../../support/utils/dav.ts'
+import { createLinkShare } from '../../support/utils/sharing.ts'
+
+test.describe('Viewer on public link shares', () => {
+	test('opens a single shared image in the viewer', async ({ user, ownerRequest, publicShare, viewerPage }) => {
+		await uploadMediaFile(ownerRequest, user, 'image1.jpg', '/image1.jpg', 'image/jpeg')
+		const share = await createLinkShare(ownerRequest, '/image1.jpg')
+
+		// A single-file public share opens the viewer automatically. On a public
+		// share the node is exposed under the share token, so we only assert the
+		// correct handler renders, not the (token) file name.
+		await publicShare.open(share.url)
+		await viewerPage.waitForOpen()
+
+		await viewerPage.expectHandler('image')
+	})
+
+	test('opens a single shared video in the viewer', async ({ user, ownerRequest, publicShare, viewerPage }) => {
+		await uploadMediaFile(ownerRequest, user, 'video1.mp4', '/video1.mp4', 'video/mp4')
+		const share = await createLinkShare(ownerRequest, '/video1.mp4')
+
+		// A single-file public share opens the viewer automatically.
+		await publicShare.open(share.url)
+		await viewerPage.waitForOpen()
+
+		await viewerPage.expectHandler('video')
+		// The public share serves the video from the public WebDAV endpoint.
+		await expect(viewerPage.mediaElement('video'))
+			.toHaveAttribute('src', new RegExp(`/public\\.php/dav/files/${share.token}`))
+	})
+
+	test('navigates through a shared folder of images', async ({ user, ownerRequest, publicShare, filesListPage, viewerPage }) => {
+		await mkdir(ownerRequest, user, '/Photos')
+		const images = ['image1.jpg', 'image2.jpg', 'image3.jpg', 'image4.jpg']
+		for (const image of images) {
+			await uploadMediaFile(ownerRequest, user, image, `/Photos/${image}`, 'image/jpeg')
+		}
+		const share = await createLinkShare(ownerRequest, '/Photos')
+
+		await publicShare.open(share.url)
+		await expect(filesListPage.getRowForFile('image1.jpg')).toBeVisible()
+
+		await filesListPage.getRowNameLinkForFile('image1.jpg').click()
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('image1.jpg')
+
+		await expect(viewerPage.nextButton).toBeVisible()
+		await expect(viewerPage.previousButton).toBeVisible()
+
+		for (const image of ['image2.jpg', 'image3.jpg', 'image4.jpg']) {
+			await viewerPage.next()
+			await viewerPage.waitForOpen()
+			expect(await viewerPage.currentName()).toBe(image)
+			await viewerPage.expectHandler('image')
+		}
+	})
+})
diff --git a/tests/playwright/e2e/viewer/sort.spec.ts b/tests/playwright/e2e/viewer/sort.spec.ts
new file mode 100644
index 0000000000000..87a8e361593a4
--- /dev/null
+++ b/tests/playwright/e2e/viewer/sort.spec.ts
@@ -0,0 +1,92 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { expect, test } from '../../support/fixtures/viewer-page.ts'
+
+// The viewer no longer sorts the list itself; it follows the order the Files
+// app provides. These guard nextcloud/viewer#2596 (underscore ordering) and
+// nextcloud/viewer#3027 (respect the active sort order).
+test.describe('Viewer follows the files list order', () => {
+	test('steps through underscore-suffixed names in list order', async ({ filesListPage, uploadMedia, openFile, viewerPage }) => {
+		// Files app natural order is name.jpg, name_1.jpg, name_2.jpg, name_3.jpg.
+		const names = ['name.jpg', 'name_1.jpg', 'name_2.jpg', 'name_3.jpg']
+		for (const name of names) {
+			await uploadMedia('image1.jpg', name, 'image/jpeg')
+		}
+		await filesListPage.open()
+
+		await openFile('name.jpg')
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe('name.jpg')
+
+		for (const name of names.slice(1)) {
+			await viewerPage.next()
+			await viewerPage.waitForOpen()
+			expect(await viewerPage.currentName()).toBe(name)
+		}
+	})
+
+	test('steps through a folder sorted by modification time, not by name', async ({ filesListPage, uploadMedia, openFile, viewerPage }) => {
+		// Names ascend a, b, c while the modification times do not, so a
+		// viewer ordering the list itself by name shows a different file
+		const day = 24 * 60 * 60
+		const now = Date.now() / 1000
+		await uploadMedia('image1.jpg', 'a.jpg', 'image/jpeg', now - day)
+		await uploadMedia('image1.jpg', 'b.jpg', 'image/jpeg', now - day * 3)
+		await uploadMedia('image1.jpg', 'c.jpg', 'image/jpeg', now - day * 2)
+		await filesListPage.open()
+
+		await filesListPage.sortByColumn('Modified')
+		await expect(filesListPage.getColumnHeader('Modified')).toHaveAttribute('aria-sort', 'ascending')
+
+		// Whatever the list shows is what the viewer has to follow, so read
+		// the order rather than assuming which end welcome.txt lands on
+		const listed = (await filesListPage.getRowNames()).filter((name) => name.endsWith('.jpg'))
+		// The sort has to disagree with the name order, or this cannot tell
+		// a viewer following the list from one sorting by name itself
+		expect(listed).not.toEqual([...listed].sort())
+
+		await openFile(listed[0]!)
+		await viewerPage.waitForOpen()
+		expect(await viewerPage.currentName()).toBe(listed[0])
+
+		for (const name of listed.slice(1)) {
+			await viewerPage.next()
+			await viewerPage.waitForOpen()
+			expect(await viewerPage.currentName()).toBe(name)
+		}
+	})
+
+	test('steps backwards through a descending sort', async ({ filesListPage, uploadMedia, openFile, viewerPage }) => {
+		for (const name of ['a.jpg', 'b.jpg', 'c.jpg']) {
+			await uploadMedia('image1.jpg', name, 'image/jpeg')
+		}
+		await filesListPage.open()
+
+		// Reversing the name order is the same list read the other way, so
+		// a viewer sorting by name on its own walks it backwards
+		await filesListPage.sortByColumn('Name')
+		await expect(filesListPage.getColumnHeader('Name')).toHaveAttribute('aria-sort', 'descending')
+
+		const listed = (await filesListPage.getRowNames()).filter((name) => name.endsWith('.jpg'))
+		expect(listed).toEqual(['c.jpg', 'b.jpg', 'a.jpg'])
+
+		await openFile(listed[0]!)
+		await viewerPage.waitForOpen()
+
+		for (const name of listed.slice(1)) {
+			await viewerPage.next()
+			await viewerPage.waitForOpen()
+			expect(await viewerPage.currentName()).toBe(name)
+		}
+
+		// And back up the same way
+		for (const name of [...listed].reverse().slice(1)) {
+			await viewerPage.previous()
+			await viewerPage.waitForOpen()
+			expect(await viewerPage.currentName()).toBe(name)
+		}
+	})
+})
diff --git a/tests/playwright/e2e/viewer/videos.spec.ts b/tests/playwright/e2e/viewer/videos.spec.ts
new file mode 100644
index 0000000000000..b7f3c6fb93e7a
--- /dev/null
+++ b/tests/playwright/e2e/viewer/videos.spec.ts
@@ -0,0 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { createMediaViewerTests, VIDEO_MEDIA } from './media.ts'
+
+createMediaViewerTests(VIDEO_MEDIA)
diff --git a/tests/playwright/start-nextcloud-server.js b/tests/playwright/start-nextcloud-server.js
index e3ec044d9a57e..cb11f51ac6226 100644
--- a/tests/playwright/start-nextcloud-server.js
+++ b/tests/playwright/start-nextcloud-server.js
@@ -50,7 +50,9 @@ async function start() {
 	}
 
 	await waitOnNextcloud(ip)
-	await configureNextcloud(process.env.PLAYWRIGHT_SETUP ? [] : ['viewer'])
+	// The viewer used to be fetched from its own repository; it now ships with
+	// the server and is enabled on install, so no app has to be provisioned.
+	await configureNextcloud([])
 
 	if (process.env.PLAYWRIGHT_SETUP) {
 		// When the apps folder is mounted, configureNextcloud writes an
diff --git a/tests/playwright/support/fixtures/viewer-page.ts b/tests/playwright/support/fixtures/viewer-page.ts
new file mode 100644
index 0000000000000..621038601954f
--- /dev/null
+++ b/tests/playwright/support/fixtures/viewer-page.ts
@@ -0,0 +1,97 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { User } from '@nextcloud/e2e-test-server'
+import type { APIRequestContext } from '@playwright/test'
+
+import { mergeTests } from '@playwright/test'
+import { readFileSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { ViewerPage } from '../sections/ViewerPage.ts'
+import { uploadContent } from '../utils/dav.ts'
+import { test as filesTest } from './files-page.ts'
+import { test as sharingTestBase } from './files-sharing-page.ts'
+import { test as publicShareTestBase } from './public-share-page.ts'
+
+/**
+ * The absolute path of a media fixture, from the shared `tests/data/media`.
+ *
+ * @param name - The fixture file name (e.g. `image1.jpg`)
+ */
+export function mediaFixturePath(name: string): string {
+	return fileURLToPath(new URL(`../../../data/media/${name}`, import.meta.url))
+}
+
+/**
+ * Upload a bundled media fixture to the user's WebDAV root.
+ *
+ * @param request - The request context to upload with (authenticated as `user`)
+ * @param user - The user owning the file
+ * @param fixture - The fixture file name to read from `tests/data/media`
+ * @param remoteName - The remote name/path relative to the user root (defaults to the fixture name)
+ * @param mimeType - The content type sent with the upload
+ * @param mtime - Modification time in seconds, to control the sort order
+ */
+export async function uploadMediaFile(
+	request: APIRequestContext,
+	user: User,
+	fixture: string,
+	remoteName: string = fixture,
+	mimeType: string = 'application/octet-stream',
+	mtime?: number,
+): Promise<void> {
+	const path = remoteName.startsWith('/') ? remoteName : `/${remoteName}`
+	await uploadContent(request, user, readFileSync(mediaFixturePath(fixture)), mimeType, path, mtime)
+}
+
+interface ViewerFixtures {
+	/** Page object for the viewer modal. */
+	viewerPage: ViewerPage
+	/** Upload a bundled media fixture to the logged-in user's root. */
+	uploadMedia: (fixture: string, remoteName?: string, mimeType?: string, mtime?: number) => Promise<void>
+	/** Open a file (or folder) by clicking its name link, triggering its default action. */
+	openFile: (name: string) => Promise<void>
+}
+
+/**
+ * The Files fixtures (logged-in random `user`, `filesListPage`) plus the viewer
+ * page object and helpers to upload media and open files into the viewer.
+ */
+export const test = mergeTests(filesTest).extend<ViewerFixtures>({
+	viewerPage: async ({ page }, use) => {
+		await use(new ViewerPage(page))
+	},
+
+	uploadMedia: async ({ page, user }, use) => {
+		await use((fixture, remoteName, mimeType, mtime) => uploadMediaFile(page.request, user, fixture, remoteName, mimeType, mtime))
+	},
+
+	openFile: async ({ filesListPage }, use) => {
+		await use((name) => filesListPage.getRowNameLinkForFile(name).click())
+	},
+})
+
+/**
+ * The public-share fixtures (guest `page`, share `owner` request) plus the
+ * viewer page object — for viewer behaviour on public link shares.
+ */
+export const publicShareTest = mergeTests(publicShareTestBase).extend<{ viewerPage: ViewerPage }>({
+	viewerPage: async ({ page }, use) => {
+		await use(new ViewerPage(page))
+	},
+})
+
+/**
+ * The user-share fixtures (`page` logged in as the recipient `user`, `owner`
+ * request context to seed and share) plus the viewer page object — for viewer
+ * behaviour on files shared with the current user.
+ */
+export const sharingTest = mergeTests(sharingTestBase).extend<{ viewerPage: ViewerPage }>({
+	viewerPage: async ({ page }, use) => {
+		await use(new ViewerPage(page))
+	},
+})
+
+export { expect } from '../matchers.ts'
diff --git a/tests/playwright/support/sections/ViewerPage.ts b/tests/playwright/support/sections/ViewerPage.ts
new file mode 100644
index 0000000000000..ebd910b30ff17
--- /dev/null
+++ b/tests/playwright/support/sections/ViewerPage.ts
@@ -0,0 +1,208 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { Locator, Page } from '@playwright/test'
+
+import { expect } from '@playwright/test'
+
+/** Media kinds handled by the viewer and their custom element tag / inner media tag. */
+export type MediaKind = 'image' | 'video' | 'audio'
+
+const HANDLER_TAG: Record<MediaKind, string> = {
+	image: 'oca-viewer-image',
+	video: 'oca-viewer-video',
+	audio: 'oca-viewer-audio',
+}
+
+const MEDIA_ELEMENT: Record<MediaKind, string> = {
+	image: 'img',
+	video: 'video',
+	audio: 'audio',
+}
+
+/**
+ * Page object for the viewer modal.
+ *
+ * The viewer mounts a `<div id="viewer">` on the body, inside which an NcModal
+ * renders with the `viewer__modal` class. The active handler is rendered as a
+ * custom element (`oca-viewer-image`, `oca-viewer-video`, `oca-viewer-audio`).
+ */
+export class ViewerPage {
+	public readonly root: Locator
+	public readonly modal: Locator
+	public readonly container: Locator
+	public readonly content: Locator
+	public readonly headerName: Locator
+	public readonly loading: Locator
+	public readonly errorMessage: Locator
+	public readonly closeButton: Locator
+	public readonly nextButton: Locator
+	public readonly previousButton: Locator
+
+	constructor(public readonly page: Page) {
+		// NcModal teleports its content to the document body, so the modal is not
+		// under the #viewer mount point — match it directly by its class + role.
+		this.root = page.locator('.viewer__modal')
+		this.modal = this.root
+		this.container = this.modal.locator('.modal-container')
+		this.content = this.modal.locator('.modal-container__content')
+		this.headerName = this.modal.locator('.modal-header__name')
+		this.loading = this.modal.locator('.viewer__loading')
+		this.errorMessage = this.modal.locator('.empty-content__name')
+		this.closeButton = this.modal.getByRole('button', { name: 'Close' })
+		this.nextButton = this.modal.getByRole('button', { name: 'Next' })
+		this.previousButton = this.modal.getByRole('button', { name: 'Previous' })
+	}
+
+	/**
+	 * Click the modal content background (outside the media), which closes the
+	 * viewer. Clicks near a corner so the centered media is never hit.
+	 */
+	public async clickOutside(): Promise<void> {
+		await this.content.click({ position: { x: 8, y: 8 } })
+	}
+
+	/**
+	 * Wait for the viewer modal to be gone.
+	 */
+	public async waitForClosed(): Promise<void> {
+		await expect(this.container).toBeHidden()
+	}
+
+	/**
+	 * Assert the viewer shows an error message and is not stuck loading.
+	 */
+	public async expectError(): Promise<void> {
+		await expect(this.errorMessage).toBeVisible()
+		await expect(this.loading).toHaveCount(0)
+	}
+
+	/**
+	 * The custom element for the given media kind.
+	 *
+	 * @param kind - The media kind
+	 */
+	public handlerTag(kind: MediaKind): Locator {
+		return this.container.locator(HANDLER_TAG[kind])
+	}
+
+	/**
+	 * The inner media element (img/video/audio) for the given media kind.
+	 *
+	 * @param kind - The media kind
+	 */
+	public mediaElement(kind: MediaKind): Locator {
+		return this.handlerTag(kind).locator(MEDIA_ELEMENT[kind])
+	}
+
+	/**
+	 * Assert the viewer modal is visible.
+	 */
+	public async isVisible(): Promise<void> {
+		await expect(this.container).toBeVisible()
+	}
+
+	/**
+	 * Wait for the viewer to be open and done loading (spinner gone).
+	 */
+	public async waitForOpen(): Promise<void> {
+		await expect(this.container).toBeVisible()
+		// Fetching and decoding the media is the slowest thing the viewer does,
+		// and the shared CI runners are slower at it than the default budget
+		// allows. The spinner going away is the signal, not how fast.
+		await expect(this.loading).toHaveCount(0, { timeout: 20_000 })
+	}
+
+	/**
+	 * The basename of the file currently shown in the header.
+	 */
+	public async currentName(): Promise<string> {
+		return (await this.headerName.textContent())?.trim() ?? ''
+	}
+
+	/**
+	 * Assert the active handler and its media element are visible for the given kind.
+	 *
+	 * @param kind - The media kind
+	 */
+	public async expectHandler(kind: MediaKind): Promise<void> {
+		await expect(this.handlerTag(kind)).toBeVisible()
+		await expect(this.mediaElement(kind)).toHaveAttribute('src', /.+/)
+	}
+
+	/**
+	 * Navigate to the next file in the slideshow.
+	 */
+	public async next(): Promise<void> {
+		await this.nextButton.click()
+	}
+
+	/**
+	 * Navigate to the previous file in the slideshow.
+	 */
+	public async previous(): Promise<void> {
+		await this.previousButton.click()
+	}
+
+	/**
+	 * Close the viewer modal.
+	 */
+	public async close(): Promise<void> {
+		await this.closeButton.click()
+		await expect(this.container).toBeHidden()
+		// Closing unwinds the history entries the viewer pushed, and the browser
+		// applies that asynchronously. Wait for it so a following assertion, or a
+		// following open, does not race the navigation still on its way.
+		await this.page.waitForURL((url) => !url.searchParams.has('openfile'))
+	}
+
+	/**
+	 * The header actions menu toggle, if the actions are collapsed into a menu.
+	 */
+	public actionsToggle(): Locator {
+		return this.modal.getByRole('button', { name: /Actions|Open actions menu/i })
+	}
+
+	/**
+	 * Run a header action by its label, opening the actions menu if needed.
+	 *
+	 * @param name - The action label (or a matching regexp)
+	 */
+	public async runAction(name: string | RegExp): Promise<void> {
+		const direct = this.modal.getByRole('button', { name })
+		if (!(await direct.isVisible())) {
+			const toggle = this.actionsToggle()
+			if (await toggle.isVisible()) {
+				await toggle.click()
+			}
+		}
+		await this.page.getByRole('menuitem', { name })
+			.or(direct)
+			.first()
+			.click()
+	}
+
+	/**
+	 * Open the Files sidebar from the viewer header actions.
+	 * The action emits `viewer:sidebar:open`, which the Files app listens to.
+	 */
+	public async openSidebar(): Promise<void> {
+		// The header actions collapse into a menu; the "Open sidebar" entry is a
+		// menuitem there. Open the menu first if the entry is not already shown.
+		const directButton = this.modal.getByRole('button', { name: 'Open sidebar' })
+		const toggle = this.actionsToggle()
+		// Both checks below are instant, so wait for the header to render one of
+		// the two entry points first - it is still loading when opened from a
+		// slow preview.
+		await expect(directButton.or(toggle).first()).toBeVisible()
+		if (!(await directButton.isVisible())) {
+			await toggle.click()
+		}
+		await this.page.getByRole('menuitem', { name: 'Open sidebar' })
+			.or(directButton)
+			.first()
+			.click()
+	}
+}