diff --git a/lib/__tests__/file-preview.test.ts b/lib/__tests__/file-preview.test.ts
index ba46bfea0..c8bfe001f 100644
--- a/lib/__tests__/file-preview.test.ts
+++ b/lib/__tests__/file-preview.test.ts
@@ -106,6 +106,21 @@ describe('previewBlobType', () => {
     expect(previewBlobType('photo.jpg', 'application/x-as400attachment', '')).toBe('image/jpeg');
   });
 
+  it('derives a viewable type from every image, audio and video extension but SVG', () => {
+    const kinds: Record<string, string[]> = {
+      image: ['jpg', 'jpeg', 'png', 'gif', 'webp', 'avif', 'bmp', 'ico'],
+      audio: ['mp3', 'wav', 'ogg', 'm4a', 'flac', 'aac', 'opus'],
+      video: ['mp4', 'webm', 'ogv', 'mov', 'm4v', 'avi', 'mkv'],
+    };
+    for (const [kind, extensions] of Object.entries(kinds)) {
+      for (const ext of extensions) {
+        const name = `file.${ext}`;
+        expect(getFilePreviewKind(name)).toBe(kind);
+        expect(previewBlobType(name, 'application/x-as400attachment', '')).toMatch(new RegExp(`^${kind}/`));
+      }
+    }
+  });
+
   it('hands the unsandboxed PDF viewer nothing but application/pdf', () => {
     // The PDF preview iframe cannot be sandboxed (the browser's PDF viewer
     // refuses to run there), so XML or XHTML declared on a .pdf must not
diff --git a/lib/file-preview.ts b/lib/file-preview.ts
index d59bd735c..e7d010ae2 100644
--- a/lib/file-preview.ts
+++ b/lib/file-preview.ts
@@ -71,9 +71,10 @@ export function isFilePreviewable(name?: string, type?: string): boolean {
   return getFilePreviewKind(name, type) !== 'unsupported';
 }
 
-// Canonical types for the extensions the preview renders from a blob. No
-// script-capable type (SVG, HTML) may appear here: the preview trusts these
-// over whatever the sender declared.
+// Canonical types for the extensions the preview renders from a blob: PDF and
+// every image, audio and video extension above except SVG. No script-capable
+// type (SVG, HTML) may appear here: the preview trusts these over whatever
+// the sender declared.
 const EXT_TO_MIME: Record<string, string> = {
   pdf: 'application/pdf',
   png: 'image/png',
@@ -83,13 +84,22 @@ const EXT_TO_MIME: Record<string, string> = {
   webp: 'image/webp',
   avif: 'image/avif',
   bmp: 'image/bmp',
+  ico: 'image/x-icon',
   mp3: 'audio/mpeg',
   wav: 'audio/wav',
   ogg: 'audio/ogg',
   m4a: 'audio/mp4',
+  flac: 'audio/flac',
+  aac: 'audio/aac',
+  // Ogg Opus (RFC 7845); audio/opus names the bare RTP payload.
+  opus: 'audio/ogg',
   mp4: 'video/mp4',
   webm: 'video/webm',
   ogv: 'video/ogg',
+  mov: 'video/quicktime',
+  m4v: 'video/mp4',
+  avi: 'video/x-msvideo',
+  mkv: 'video/x-matroska',
 };
 
 const GENERIC_MIME_TYPES = new Set(['', 'application/octet-stream', 'binary/octet-stream']);