MP4 File Format (.mp4)
An MP4 file holds video, audio, subtitle and chapter tracks together in the MPEG-4 Part 14 container, the structure ISO standardised from Apple's QuickTime format and the way most video is stored and shared today.
MP4 at a glance#
| Full name | MPEG-4 Part 14 |
|---|---|
| File extension | .mp4 |
| Category | Video Files |
| Developer | ISO/IEC MPEG (Moving Picture Experts Group) |
| First released | 2001 |
| MIME types | video/mp4audio/mp4application/mp4 |
| Compression | Varies from file to file |
| Specification | ISO/IEC 14496-14 (MPEG-4 Part 14) |
| FileFlip support | FileFlip reads and writes this format |
What a .mp4 file can hold#
These are the things a MP4 file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.
| Embedded metadata | Yes |
|---|---|
| High dynamic range | Yes |
| Audio | Yes |
| Video | Yes |
| Subtitle tracks | Yes |
| Chapters | Yes |
| Encryption | Yes |
| Streaming | Yes |
Strengths and limitations of MP4#
What MP4 does well
- An MP4 carrying H.264 plays on essentially every phone, browser, console and smart TV sold in the last fifteen years
- Hardware decoders for H.264 and H.265 sit in most chips, so playback barely touches the CPU or the battery
- Shares its box structure with MOV, so moving between the two copies the streams across without re-encoding
- Fragmented MP4 is the segment format behind DASH and HLS, which is what YouTube and Netflix deliver
Where MP4 falls short
- The extension says nothing about whether a given player can decode what is inside
- H.265 inside an MP4 will not play in Chrome or Firefox on machines without hardware HEVC decode
- Subtitle tracks are carried but plenty of players ignore them, where Matroska subtitles are read almost everywhere
- Files using Common Encryption or FairPlay open only in software licensed to decrypt them
Choose MP4 when the file has to play somewhere you do not control, which covers anything uploaded, emailed or handed to another person.
Convert an MP4 to something else when the destination is not a player: pulling out the audio, making a GIF, or moving into Matroska to keep several subtitle and audio tracks in one file.
How to open a .mp4 file#
A .mp4 file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts MP4 into a format your machine already opens, and it does it in the browser tab rather than on a server.
| Platform | Programs that open it |
|---|---|
| Windows | VLC, Films & TV, Windows Media Player, MPC-HC |
| macOS | QuickTime Player, VLC, IINA |
| Linux | VLC, mpv, GNOME Videos |
| iOS | Photos, Files, VLC |
| Android | Google Photos, VLC, MX Player |
| Web | FileFlip |
MP4 questions people ask#
Is MP4 a video format or a codec?
MP4 is a container, not a codec. It is a wrapper holding video, audio and subtitle streams side by side, and the codec inside decides whether a device can actually decode it. Two MP4 files can behave completely differently: one holding H.264 plays everywhere, one holding H.265 or AV1 may not play at all on older hardware.
Why won't my MP4 file play?
An MP4 that refuses to play is almost always carrying a codec the player cannot decode rather than being damaged. H.265 and AV1 are the usual culprits, since both need recent hardware or software support, and some MP4s from streaming services are encrypted and will only open in an authorised app. Re-encoding the video to H.264 fixes nearly all of these.
Does converting MKV to MP4 lose quality?
Converting MKV to MP4 loses nothing at all when the video is already H.264 or H.265 with AAC audio, because the streams are lifted out of one container and dropped into the other untouched. That is a remux, and it runs at disk speed. Quality only drops when the codec has to change, for example a VP9 video that MP4 players do not expect, which forces a full re-encode.
What is the difference between MP4 and MOV?
MP4 was standardised from Apple's QuickTime file format, which is what a MOV file uses, so the two share the same underlying atom structure. In practice this means an H.264 video in a MOV and the same video in an MP4 are the same bytes in a slightly different wrapper, and converting between them is a fast remux rather than a re-encode. MOV also carries codecs MP4 does not, ProRes being the common one.
Does MP4 support subtitles and chapters?
MP4 carries both, subtitles as timed text tracks and chapters as a chapter track, but player support is uneven. QuickTime and VLC read them, plenty of smart TVs and browsers ignore them, and many encoders never write chapters in the first place. Subtitles delivered as a separate SRT file alongside the MP4 are more reliably picked up.
Converting MP4 files#
Convert MP4 to another format
Convert another format to MP4
Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.