fix(mime): prefer video/mp4 for .mp4 and image/x-icon for .ico

packages/mime/.changes/patch.prefer-common-mime-types.md

@@ -0,0 +1 @@
+Prefer `video/mp4` for `.mp4` files and `image/x-icon` for `.ico` files.

packages/mime/scripts/codegen.ts

@@ -81,6 +81,19 @@ export function generateMimeTypesContent(): string {
     }
   }
 
+  // Manual overrides for extensions where the codegen picks an uncommon type.
+  // See https://github.com/remix-run/remix/issues/11106 (mp4)
+  // See https://github.com/remix-run/remix/issues/11107 (ico)
+  let preferredOverrides: Record<string, string> = {
+    // RFC 4337 §2: video/mp4 is the general-purpose type for .mp4 files
+    mp4: 'video/mp4',
+    // image/x-icon is historically used by Microsoft and browsers
+    ico: 'image/x-icon',
+  }
+  for (let [ext, mimeType] of Object.entries(preferredOverrides)) {
+    extensionMap[ext] = mimeType
+  }
+
   // Sort by extension for consistent output
   let sortedExtensions = Object.keys(extensionMap).sort()
   let entries = sortedExtensions.map((ext) => `  ${formatKey(ext)}: '${extensionMap[ext]}',`)

packages/mime/src/generated/mime-types.ts

@@ -403,7 +403,7 @@ export let mimeTypes: Record<string, string> = {
   icc: 'application/vnd.iccprofile',
   ice: 'x-conference/x-cooltalk',
   icm: 'application/vnd.iccprofile',
-  ico: 'image/vnd.microsoft.icon',
+  ico: 'image/x-icon',
   ics: 'text/calendar',
   ief: 'image/ief',
   ifb: 'text/calendar',
@@ -598,7 +598,7 @@ export let mimeTypes: Record<string, string> = {
   mp21: 'application/mp21',
   mp2a: 'audio/mpeg',
   mp3: 'audio/mpeg',
-  mp4: 'application/mp4',
+  mp4: 'video/mp4',
   mp4a: 'audio/mp4',
   mp4s: 'application/mp4',
   mp4v: 'video/mp4',

packages/mime/src/lib/detect-mime-type.test.ts

@@ -74,10 +74,11 @@ describe('detectMimeType()', () => {
     assert.equal(detectMimeType('gif'), 'image/gif')
     assert.equal(detectMimeType('svg'), 'image/svg+xml')
     assert.equal(detectMimeType('webp'), 'image/webp')
+    assert.equal(detectMimeType('ico'), 'image/x-icon')
   })
 
   it('returns MIME type for common video formats', () => {
-    assert.equal(detectMimeType('mp4'), 'application/mp4')
+    assert.equal(detectMimeType('mp4'), 'video/mp4')
     assert.equal(detectMimeType('webm'), 'video/webm')
     assert.equal(detectMimeType('mov'), 'video/quicktime')
   })