Containers and codecs: the key idea
MP4, MOV, WebM and MKV are containers: boxes that hold video, sound and extra information. The codec is how the video inside is compressed, such as H.264, HEVC (H.265), VP9 or AV1. Whether a file plays depends on both. An MP4 with H.264 plays almost anywhere; an MP4 with AV1 may not play on older devices.
Formats compared
| Format | Made by | Usual codecs | Plays on | Best for |
|---|---|---|---|---|
| MP4 | International standard | H.264, HEVC, AV1 | Practically everything | Sharing, uploading, phones, TVs |
| MOV | Apple | H.264, HEVC, ProRes | Apple devices; most others with H.264 | iPhone recording, Mac editing |
| WebM | Open, royalty-free | VP8, VP9, AV1 | Browsers; patchy elsewhere | Videos on websites |
| MKV | Open (Matroska) | Almost anything | Media players; few phones or editors | Recording (crash-safe), archiving |
MP4: the safe default
MP4 with H.264 video and AAC sound plays on iPhones, Android phones, Windows, Macs, smart TVs, games consoles, and every major website and app. If you don’t know where a video will be watched, choose MP4. It’s what FitVideo produces from every tool.
MOV: great on Apple, awkward elsewhere
MOV is Apple’s QuickTime format and the one iPhones save. MP4 was based on it, so the two are closely related, and a MOV with H.264 inside usually converts to MP4 instantly without re-encoding. Problems start when the MOV contains HEVC, which many Windows PCs and editors can’t play. See why iPhone videos won’t play on Windows.
WebM: built for the web
WebM is open and royalty-free, so browsers can record and play it without licensing fees. That’s why browser screen recorders and meeting tools often save WebM. It plays perfectly in Chrome, Firefox and Edge but is often rejected by phones’ galleries, editors and upload forms. Convert it with the WebM to MP4 converter.
MKV: for recording
MKV survives crashes: if the recording program or computer fails, the file is still readable up to that moment. That’s why OBS records to MKV by default. For sharing or editing, convert to MP4; when the video inside is H.264 or HEVC, the MKV to MP4 converter repackages it in seconds.
Which format is smallest?
The container barely affects size; the codec and bitrate do. AV1 and HEVC are the most efficient, then VP9, then H.264. But a smaller file that won’t play isn’t useful, so for sharing, use MP4 with H.264 and control the size with the bitrate. The guide to reducing video size explains how.
Which format should you use?
| You want to… | Use |
|---|---|
| Send a video to anyone | MP4 (H.264) |
| Upload to social media or a form | MP4 (H.264) |
| Edit on a Mac | MOV or MP4 |
| Put a video on your own website | MP4, optionally with WebM as well |
| Record gameplay or a long stream | MKV, then convert to MP4 |
| Save only the sound | MP3 |
How to convert between formats
To get an MP4 from any of these, use the video converter. It repackages the file in seconds when the video inside is already H.264 or HEVC, and re-encodes it to H.264 when it isn’t. Nothing is uploaded, and there’s no watermark. To save only the sound from a video, choose MP3 instead.
What about the sound?
Containers hold sound too. MP4 and MOV usually carry AAC sound, which everything plays; WebM uses Opus or Vorbis, which some devices don’t. When FitVideo converts to MP4, it also converts the sound to AAC when needed, so the result plays with sound everywhere.
Free toolTry it now: Video converter Any video to MP4Questions
Is MP4 better than MOV?
For sharing, yes: MP4 plays on more devices. For editing on a Mac, MOV is just as good.
Does converting MOV to MP4 lose quality?
Not when the video inside is H.264 or HEVC; it’s repackaged without re-encoding.
Is WebM better than MP4?
For websites it’s efficient and royalty-free, but MP4 is far more widely supported elsewhere.
What is the best video format for WhatsApp?
MP4 with H.264 video and AAC sound.
What format do iPhones record in?
MOV files, usually with HEVC video, unless the camera is set to Most Compatible.