Choose a file to convert. It's processed locally — never uploaded. Tip: add several files to convert them all at once.
Result appears here after you select
{ } How to use
- Choose the MP4.
- Select Process. Expect this one to be slow — VP9 encoding in the browser takes far longer than H.264.
- Download the WebM.
{ } How it works
MP4 to WebM works on the file you upload. Select Process ▸ and it runs entirely in your browser — nothing is uploaded to a server — then shows the result in the Output panel.
Input
- Video file — upload a file (video/*); it is read locally in your browser
Output
A downloadable WEBM file — use the Download button in the Output panel.
{ } Common uses
- Serve video on a web page in an open, royalty-free format.
- Get a smaller file than H.264 at a comparable picture quality.
- Publish somewhere that prefers or requires WebM.
{ } Limitations
- The video bitrate is fixed at 1 Mbit/s whatever comes in. That is a fair target for 720p, generous for 480p and far too low for 1080p or 4K, so a high-resolution clip comes out soft. Resize it down first if the result disappoints.
- VP9 in WebAssembly is slow — several times slower than the H.264 tools here, without the hardware encoder your device has for H.264. More than a minute or two of footage is a long wait.
- The audio is re-encoded to Opus at the encoder’s default rate, and no audio setting is exposed.
{ } FAQ
Is my data uploaded to a server?
No. Everything runs locally in your browser — your files never leave your device.
Can I process more than one file at once?
Yes — add several files and they’re all processed and downloaded together as a ZIP.
Is this tool free?
Yes — it’s completely free and needs no sign-up.
Why does this take so much longer than the other conversions?
Because VP9 is a far heavier encoder than H.264, and this one runs single-threaded in WebAssembly rather than on the video hardware your device would use for H.264. You get a smaller file for the same quality and you pay for it in time.