MP4
Also known as: MPEG-4, .mp4, mp4 file, MPEG-4 Part 14
MP4 (MPEG-4 Part 14) is the most common video container format. The .mp4 file holds video, audio, and subtitle streams together, but does not itself define quality — the codec inside (usually H.264 or HEVC) decides how large and how compressed the video is.
- A container format, not a compression method
- Usually holds H.264 or HEVC video inside
- The most widely compatible video file type
A container, not a codec
MP4 is a container: a wrapper that packages a video track, one or more audio tracks, and sometimes captions into a single file. It says nothing about how the video is compressed — that is the job of the codec stored inside.
This is why two .mp4 files of the same clip can differ wildly in size. One might use older H.264 compression; another might use HEVC (H.265), which stores the same footage in roughly half the space.
Why MP4 is everywhere
MP4 plays on virtually every phone, browser, TV, and editing app, which is why it is the default share and export format for most cameras and apps. iPhones record in .mov but export to .mp4 when you share to non-Apple destinations.
For storage, the takeaway is that video — MP4 or otherwise — is almost always the single largest category on a full device. Re-compressing long clips to HEVC, or removing ones you have already backed up, frees far more space than tidying photos.