How to convert MKV to WEBM
- Add your .MKV file - drop it in the box above or click to browse.
- Convert it to .WEBM in a few seconds.
- Download your new .WEBM file.
What to expect
- Most MKV files in the wild (movie rips, screen recordings, Blu-ray remuxes) use H.264 or H.265 video with AAC or AC-3 audio, so lossless remux is rarely possible - re-encoding is the norm.
- VP9 encoding is slow: a one-hour file can take 30-90 minutes on a typical PC; adding
-cpu-used 4to the FFmpeg command trades a little quality for much faster output. - WEBM does not support subtitle tracks, chapters, or multiple named audio tracks - these are silently dropped during conversion.
Frequently asked questions
Can I convert MKV to WEBM without losing quality?
Only if the MKV already contains VP9 or AV1 video with Vorbis or Opus audio - in that case
ffmpeg -i input.mkv -c copy output.webm is lossless. Any other codec combination requires re-encoding with some quality loss.Will the WEBM file play in all browsers?
Chrome, Firefox, and Edge support WEBM natively. Safari has supported VP9 since version 16 (2022), so coverage is now very broad.
Why does my converted WEBM have no audio?
FFmpeg may have silently dropped an unsupported audio track. Re-run the command with
-c:a libopus to re-encode the audio to Opus instead of dropping it.What happens to subtitles and chapters from the MKV?
The WEBM container does not support subtitle tracks, chapters, or font attachments - they are removed during conversion. Burn subtitles into the video beforehand if you need them preserved.
