Convert MP4 to WEBM
Convert MP4 files to WEBM entirely in your browser — no upload, no account, no watermark.
Your file never leaves your device — conversion runs entirely in this browser tab.
To convert MP4 to WEBM, open the WEBM converter and drop your MP4 file in. The conversion runs entirely inside your browser using WebAssembly, so the file is never uploaded. Worth doing for self-hosted web video, where VP9 delivers similar quality in 30–50% fewer bits.
What to expect from this conversion
Worth doing for self-hosted web video, where VP9 delivers similar quality in 30–50% fewer bits. Budget real time for it: VP9 is a far slower encoder than H.264, and in a browser that penalty compounds. Serve an MP4 fallback for Safari and TVs.
The universal container, normally holding H.264 and AAC. Plays essentially everywhere.
Lossy · video
Google’s open container, normally holding VP9 video and Opus audio. Excellent in browsers, poor on TVs and in editors.
Lossy · video
Both MP4 and WEBM discard data to save space, so this conversion compresses something that has already been compressed. Always convert from your original file rather than from an earlier conversion — the losses compound.
How to do it
- Open the WEBM converter
Go to the WEBM converter and drop your MP4 file onto it, or click to browse.
- Convert
Press Convert. FFmpeg runs in your browser and shows real progress as it works.
- Download
Download the finished WEBM file. It is created in your browser and never sent anywhere.
Common questions
How do I convert MP4 to WEBM?
Open the WEBM converter, drop your MP4 file onto it and press Convert. Everything runs in your browser — the file is not uploaded. Desktop browsers handle files up to about 200MB; mobile browsers about 40MB.
Does converting MP4 to WEBM lose quality?
Yes, some. Both MP4 and WEBM are lossy, so this is a second compression pass over data that was already compressed. The loss is usually modest, but always convert from your original rather than from a previous conversion.
Is it free to convert MP4 to WEBM?
Yes, with no account, no watermark and no daily limit. The processing happens on your device rather than on a server, so there are no per-conversion costs to pass on.
Are my files uploaded when converting MP4 to WEBM?
No. FFmpeg runs as WebAssembly inside your browser tab. The file is read from your disk, processed in memory and written back out — it never reaches a server.