WebM vs MP4
| Property | WebM | MP4 |
|---|---|---|
| Full name | WebM (based on Matroska) | MPEG-4 Part 14 |
| File extensions | .webm | .mp4, .m4v |
| Created by | MPEG (ISO/IEC 14496-14) | |
| Introduced | 2010 | 2003 |
| Compression | Lossy (VP8, VP9 or AV1) | Depends on the codec inside; usually lossy |
| Codecs inside | VP8, VP9 or AV1 video; Vorbis or Opus audio | Usually H.264 or H.265 video with AAC audio |
| Opens on | Every current browser and Android; many editors, older iPhones and TVs do not play it | Every phone, computer, TV, browser, editor and social network |
| Best for | Video on websites and browser screen recordings | Sharing, uploading and playing video anywhere |
Why convert WebM to MP4?
WebM is what browsers produce when they record: screen recorders, webcam and voice recorders built on the MediaRecorder API, many online meeting tools and a lot of downloaded web video use it. It plays in Chrome and Firefox, but iPhone apps, PowerPoint, many editors and some upload forms reject it.
Unlike MOV or MKV, a WebM almost never contains H.264, so converting means re-encoding the video. The tool uses your device's hardware H.264 encoder when it has one, which is fast on most laptops and phones. Screen recordings convert particularly well: large still areas compress easily, and the MP4 is often similar in size to the WebM.
Browser recordings often lack duration information, so players cannot show their length or seek properly. The MP4 is written with a full index and duration, which usually fixes both. If you recorded the screen with our Screen Recorder, you can trim the result afterwards with Trim Video.