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What is a WebM file?
WebM is a royalty-free video container introduced by Google in 2010, normally carrying VP8, VP9 or AV1 video with Vorbis or Opus audio. At the same visual quality it is usually smaller than an H.264 MP4, and it supports true alpha transparency, which MP4 in practice does not.
At a glance
- Full name
- WebM
- Extensions
- .webm
- Type
- Video
- Introduced
- 2010
- Created by
- Compression
- Lossy
- MIME type
- video/webm
Strengths
- Royalty-free, with no codec licensing to consider
- Smaller than H.264 MP4 at equivalent quality
- Supports video with an alpha (transparency) channel
Limitations
- Weaker support in desktop editors and on older Apple hardware
- VP9 and AV1 encoding is slower than H.264
When to use WebM
Use it when
Web delivery you control, especially if you need transparency or want to avoid codec licensing.
Avoid it when
The file goes to a client, a video editor, or an unknown device. Use MP4.
Convert WebM files
Every tool below runs in your browser unless it is labelled otherwise, so the file stays on your device.
WebM conversions
Each page states what the target format cannot carry before you run it.
WebM compared
Related video formats
Last updated 2026-08-03