MP4 vs MOV vs AVI: which video format should you use?
Short answer: MP4, MOV and AVI are containers: boxes that hold video and audio encoded with a codec. MP4 with H.264 video and AAC audio plays on virtually every phone, browser, TV and upload form, so it is the format to share in. MOV is Apple's format and plays best on Apple devices; AVI is a 1990s Windows format that modern players often refuse. Converting either to MP4 usually fixes playback problems.
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Containers and codecs: the key idea
A video file has two layers. The container — MP4, MOV, AVI — is the file format: a box holding the video, the audio and some information about them. The codec — H.264, HEVC, ProRes, DivX — is how the pictures and sound inside the box are actually compressed.
Most playback problems are codec problems wearing a container's name. A MOV holding H.264 plays almost anywhere; a MOV holding ProRes plays in editing software and little else. An AVI holding a codec from 2003 may not play at all on a modern phone. Converting to MP4 fixes this because it re-encodes the video into a codec everything supports, not because of the box itself.
The three formats compared
| MP4 | MOV | AVI | |
|---|---|---|---|
| Origin | International standard (MPEG-4) | Apple QuickTime | Microsoft, 1992 |
| Usual codecs | H.264 or HEVC with AAC audio | H.264, HEVC, ProRes | Anything — often DivX or Xvid |
| Plays in browsers | Yes | Patchy | No |
| Phones and TVs | Virtually all | Apple devices; patchy elsewhere | Often not |
| Upload sites and forms | Accepted almost everywhere | Often accepted | Often rejected |
| Best for | Sharing and playing anywhere | Recording and editing on Apple devices | Old archives only |
MOV: Apple's format
iPhones and Final Cut Pro save MOV files. They play well on Apple devices and cause friction elsewhere — on some Windows PCs, Android phones, smart TVs and upload forms. MOV to MP4 converts to H.264 video with AAC audio and keeps the original resolution by default.
The MP4 is often much smaller, because Apple devices and editing apps frequently save MOV with very little compression. The exception is recent iPhone footage recorded in High Efficiency mode, which is already HEVC-compressed: converting that to the more compatible H.264 can make the file somewhat larger. Scaling down to 1080p or 720p brings it back down.
To have an iPhone record in a more compatible format from the start, go to Settings → Camera → Formats and choose Most Compatible. Videos are then recorded as H.264, at the cost of larger files.
AVI: the one to retire
AVI dates from 1992. It can hold almost any codec, including long-obsolete ones like DivX and Indeo that modern players no longer include, and it has no browser support. It is typically found in old camera footage, downloaded films from the 2000s and legacy Windows software.
AVI to MP4 re-encodes to H.264 and AAC, and the result is frequently 50–80% smaller at the same visual quality, because older encoders were far less efficient. Conversion changes the format, not the source: footage recorded at 480p stays 480p, and interlaced camcorder footage keeps its interlacing.
MP4: the format to share in
MP4 with H.264 video and AAC audio is the most widely supported video pairing there is. It plays in every modern browser, on every phone, on smart TVs and games consoles, and it is what video sites, social networks, messaging apps and email clients expect. If you do not know what the person receiving a video uses, send MP4.
From an MP4 you can also make a GIF of a short clip, or extract the audio as MP3 when you only need the sound — a lecture or an interview, say.