MP4 MIME Type

About MP4 video files

The most widely supported video format, usually H.264 video with AAC audio. For playback to start before the whole file has downloaded, the index (the moov box) must be at the start of the file: encode with ffmpeg -movflags +faststart. The server must also answer range requests, or seeking won’t work and Safari may refuse to play.

Other types seen for these files: video/x-m4v . Accept them when reading uploads, but send video/mp4 yourself.

File signature

MP4 files start with "ftyp" at byte 4, followed by a brand such as isom, mp42 or avc1. The extension and the type a browser reports for an upload both come from the file name, so check these bytes on the server before trusting a file.

Serve .mp4 with the right Content-Type

Content-Type: video/mp4

video/mp4 mp4 m4v;

AddType video/mp4 .mp4 .m4v

@mp4 path *.mp4 *.m4v
header @mp4 Content-Type "video/mp4"

curl -sI https://example.com/file.mp4 | grep -i '^content-type'
# Content-Type: video/mp4

Set the type in code

res.set('Content-Type', 'video/mp4');
// Or make the browser download it:
res.attachment('file.mp4');

import mimetypes

mimetypes.add_type('video/mp4', '.mp4')  # if your system doesn't know it
mimetypes.guess_type('file.mp4')[0]  # 'video/mp4'

mime.AddExtensionType(".mp4", "video/mp4")
w.Header().Set("Content-Type", "video/mp4")

Accept .mp4 uploads

<input type="file" accept=".mp4,.m4v,video/mp4">

The accept attribute only filters the file picker; users can still choose another file. Listing the extension as well as the type matters, because operating systems don’t always report the type you expect.

Related types

• .webm (video/webm): WebM video
• .mov (video/quicktime): QuickTime video
• .m3u8 (application/vnd.apple.mpegurl): HLS playlist
• .m4a (audio/mp4): M4A audio

More video

.avi , .mkv , .ts . Look up any extension or type with the MIME type lookup.

Sources

• IANA registration: video/mp4
• MDN: Common media types

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Frequently asked questions