Convert MKV to WEBM
Convert MKV 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 MKV to WEBM, open the WEBM converter and drop your MKV file in. The conversion runs entirely inside your browser using WebAssembly, so the file is never uploaded. Both are Matroska-derived, so the containers are close cousins.
What to expect from this conversion
Both are Matroska-derived, so the containers are close cousins. But WEBM only permits VP8, VP9 or AV1 video with Vorbis or Opus audio, so an MKV holding H.264 still needs a full re-encode.
Matroska, an open container that can hold almost any codec plus multiple audio and subtitle tracks. Flexible, but unevenly supported.
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 MKV 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 MKV 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 MKV to WEBM?
Open the WEBM converter, drop your MKV 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 MKV to WEBM lose quality?
Yes, some. Both MKV 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 MKV 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 MKV 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.