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MP4 to WebM (VP9) - Online Video Converter
Convert MP4 to WebM (VP9) online. Private, client-side - no uploadrequired. Batch conversion, quality presets, codec control.
Convert MP4 to WebM (VP9)
Drop MP4 video here or click to select
MP4
WebM (VP9) (VP9 / Opus)
About MP4 to WebM (VP9)
MP4 pairs H.264 with AAC, so WebM re-encodes to VP9 with Opus for open web playback.
Why convert MP4 to WebM (VP9)?
- Smaller files with WebM lossy compression.
- Keep animation and transparency where supported.
- Private, no upload - runs in your browser.
MP4 vs WebM (VP9)
| Animation | Yes | Yes |
|---|---|---|
| Transparency | No | Yes |
| Compression | lossy | lossy |
| Typical use | MP4 pairs H.264 video with AAC audio in the ISO base media container. | WebM pairs VP9 video with Opus audio and supports an alpha channel. |
When not to convert MP4 to WebM (VP9)
- Skip WebM for archival masters: lossy compression discards detail, so keep the MP4 original.
- Keep a master copy: repeated exports stack small losses, so archive MP4 before batch WebM shares.
Limits
Starting point: MP4 - H.264 video with AAC audio in one file. H.264 has no alpha channel, so transparency is dropped. Apple editors accept it unevenly; keep MP4 for editing round-trips. Encode WebM (VP9 / Opus) from MP4 at a bitrate near the source, and confirm the audio track before converting.
How conversion works
Conversion runs entirely in your browser with FFmpeg WASM. Files never leave your device.
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FAQ
How do I convert MP4 to WebM (VP9)?
Drop your MP4 file onto this page, choose quality and codec settings, then click Convert. The result downloads as WebM (VP9) instantly. All processing runs in your browser.
What codec is used for WebM (VP9)?
The default codec for WebM (VP9) is VP9 / Opus. You can change the video and audio codec in Advanced mode.
Does MP4 to WebM keep quality?
Roughly, at matched bitrates; VP9 needs fewer bits than H.264 for similar detail.
Does MP4 to WebM keep audio?
Yes; AAC re-encodes to Opus unless you drop the track.
How do you store my files?
We do not store any processed videos. All conversion happens entirely in your browser using FFmpeg WASM.