Convert MP4 to WebM
Free online converter for MP4 files. Open, royalty-free format optimised for the web. Nothing to install, no watermark, and every file is deleted automatically.
Drag and drop your files
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Upload a MP4 file to convert it to WebM. Up to 3 files at once, 100 MB each.
Free · up to 3 files · 100 MB each · files deleted automatically after 1 hour.
About MP4 and WEBM
MP4 .mp4
The universal video container, normally holding H.264 video and AAC audio. If a device plays video at all, it plays MP4.
Good for
- Plays on effectively every device, browser and editor
- Excellent compression at high quality
- Streams well, and seeks quickly
Trade-offs
- H.264 carries patent licensing obligations
- Lossy — quality drops each time it is re-encoded
- Less flexible than MKV for subtitles and multiple tracks
video/mp4
WebM .webm
An open container built for the web, holding VP8, VP9 or AV1 video with Vorbis or Opus audio. Royalty-free by design.
Good for
- Open and royalty-free
- Smaller than H.264 MP4 at similar quality
- Supports transparency, which MP4 does not
Trade-offs
- Weaker support in desktop editors and older devices
- Slower to encode than H.264
- Not the safe choice for sending a file to someone
video/webm
MP4 and WEBM side by side
| MP4 | WEBM | |
|---|---|---|
| Compression | Lossy (usually H.264) | Lossy (VP9 or AV1) |
| Transparency | No | Yes — with VP9 or AV1 |
| Typically used for | Everything — the safe default for video | Web video, background loops with transparency |
What changes when you convert MP4 to WEBM
MP4 and WEBM are unrelated containers
MP4 is built on the ISO base media format, derived from QuickTime. WEBM is a deliberately narrow subset of Matroska. A container is a box, not a compression method: what decides how a video looks and how large it is, is the codec stored inside, and these two boxes accept different ones.
This is a re-encode, not a repackage
Some tools can move a stream into a different container untouched when the codecs happen to line up. We do not — every job here is decoded and encoded again, so the conversion takes time in proportion to the length of the file and costs a small amount of quality even where a repackage would have been possible. In exchange the output is predictable: it plays everywhere, rather than inheriting whatever the source happened to contain.
What your WEBM will contain
The output is VP9 video with Opus audio — both are royalty-free, which is the reason WebM exists — VP9 encodes considerably slower than H.264, so expect a longer wait than the same clip as MP4.
Other MP4 conversions
Other ways to get WebM
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