Container format comparison
WebM vs MP4
WebM exists because Google wanted a royalty-free container with royalty-free codecs (VP9/AV1 + Opus). MP4 has the universal compatibility advantage — every device made plays it. WebM is the better web-native format with smaller files; MP4 is the safer choice for everything else.
Side-by-side
| Feature | WebM | MP4 | Winner |
|---|---|---|---|
| Compatibility | Modern browsers + some apps | Universal | MP4 |
| Codec pairing (default) | VP9/AV1 + Opus | H.264/H.265 + AAC | Tied |
| File size at same content | ~10% smaller | Baseline | WebM |
| iOS native | Since iOS 14.5 | Since iOS 1 | MP4 |
| Smart TV native | Patchy | Universal | MP4 |
| YouTube serves it | Yes (modern flow) | Yes (compatibility flow) | Tied |
| Editing software | Major NLEs support it | Universal | MP4 |
WebM wins on
- Royalty-free container with royalty-free codec pairing.
- Native browser support across all modern browsers.
- Slightly smaller files at the same content.
- YouTube's default for modern variant streams.
MP4 wins on
- Universal device compatibility — every device since ~2005.
- Native iOS / Apple ecosystem.
- Smart TV + streaming stick compatibility.
- Standard for editing software, broadcast, archival.
Verdict
For web embedding + modern browser viewing: WebM is smaller and equivalent quality. For everything else (sharing files, editing, mobile playback on older devices, smart TVs): MP4. VidPickr defaults to MP4 for downloads precisely because of the compatibility advantage; WebM is available when you specifically want the smaller file.
Frequently asked
Will WebM play on an iPhone?
On iOS 14.5+, yes natively. Older iOS requires a third-party player. Most other consumer devices made in the last 5 years play WebM, but compatibility is patchier than MP4.