MKV to WebM Converter
Convert MKV to WebM free — no upload, no signup
To convert MKV to WebM, drop your MKV video into the box below and click Convert. Fylo converts with ffmpeg running inside your browser, so nothing is uploaded and there's no signup or watermark. VP8/VP9 MKVs are repackaged; others are re-encoded to VP8.
Drop videos here
or tap to browse · paste with Ctrl+V · add many at once
Your files never leave your device
If the video already uses codecs that fit the new format, Fylo repackages it instantly with no quality loss.
Advanced
How to convert MKV to WebM
Add your MKV videos
Drag and drop MKV files into the box or tap to choose them. The converter engine (about 31 MB) downloads once, the first time you convert.
Choose quality (optional)
Balanced quality suits most videos. If the codecs already fit WebM, Fylo repackages the file instead of re-encoding it, with no quality loss.
Convert and download
Click Convert, then download each WebM file or all of them as one ZIP.
Why convert MKV to WebM?
WebM is a restricted form of Matroska for the web. Converting lets you embed an MKV clip directly in a web page.
What happens when you convert MKV to WebM?
If the MKV already holds VP8, VP9 or AV1 video with Opus or Vorbis audio, Fylo repackages it losslessly. Otherwise the video is re-encoded to VP8 and the audio to Vorbis.
How does Fylo convert MKV to WebM?
Fylo reads the MKV with ffmpeg compiled to WebAssembly and writes VP8 with Vorbis audio, using libvpx's real-time preset so encoding stays practical in a browser. If the MKV already holds VP8/VP9/AV1 video with Opus or Vorbis audio, it's repackaged losslessly; otherwise it's re-encoded. Only the first video and audio track are kept, and the original resolution is preserved unless you pick 1080p, 720p or 480p under Advanced.
What's the difference between MKV and WebM?
MKV is the Matroska container, an open standard first released in 2002. It can hold virtually any video, audio or subtitle codec, and any number of tracks — so one file can carry several languages, director's commentary and subtitles. WebM is a restricted subset of Matroska.
WebM was announced by Google in 2010 as an open, royalty-free alternative to H.264 for HTML5 video. It's a subset of Matroska restricted to VP8, VP9 or AV1 video and Vorbis or Opus audio. Browser screen recorders and many web tools save WebM by default.
Learn more: MKV format guide · WebM format guide
| Property | MKV | WebM |
|---|---|---|
| Developed by | Matroska project (open standard) | |
| Introduced | 2002 | 2010 |
| Typical video codecs | Any: H.264, HEVC, VP9, AV1… | VP8, VP9, AV1 |
| Typical audio codecs | Any: AAC, Opus, FLAC, DTS, AC-3… | Vorbis, Opus |
| Plays in web browsers | Partly (Chrome/Edge for some codecs) | Yes — Chrome, Edge, Firefox, Safari 14.1+ |
| Compatibility | VLC, Plex, Kodi, most smart TVs; not iPhone or many editors | Browsers, Android; limited in editors and on iPhone apps |
| Best for | Movies with multiple audio and subtitle tracks | Royalty-free web video, screen recordings |
Frequently asked questions
Is WebM just MKV?
Essentially, yes — WebM is a Matroska subset that only allows web-friendly codecs.
Will subtitles carry over?
No, the WebM contains only the first video and audio track.
Is my MKV file uploaded to a server?
No. Fylo runs ffmpeg, the same engine used by professional video tools, compiled to WebAssembly inside your browser. Your MKV file is read directly from your device and never sent anywhere.
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