Convert MKV to WebM for websites, phones and social media. Free, fast and private: the conversion happens in your browser.
Drop video files here
or paste them, or click to choose — several files at once
Choose videosMP4, MOV, WebM, MKV, AVI, WMV, FLV, 3GP, MPEG, GIF and more · up to 1 GB per file
The video engine (about 30 MB) is downloaded once and then cached. Your videos never leave your device; long or HD videos can take a few minutes.
Drop the MKV video onto the page, paste it, or click to choose. It is read directly from your device.
Everything is set up for WebM. Adjust the size or other options if you like — the defaults suit most videos.
The conversion runs in your browser. When it is finished, save the WebM file to your device.
Matroska Video
The flexible all-in-one container
MKV (Matroska) can hold almost any video and audio codec plus several audio tracks, subtitles and chapters in a single file.
WebM (VP8/VP9 + Opus/Vorbis)
The open web video format
WebM is a royalty-free format by Google with VP8, VP9 or AV1 video and Opus or Vorbis audio, built for the web and HTML5 video.
Family clips, screen recordings and work videos never leave your device. There is no server copy to leak or delete.
No account, no watermark, no daily limits and no waiting queue. Only your device's memory sets the limit.
When the streams already fit the target format they are copied without re-encoding: done in seconds with zero quality loss.
Add your MKV file to the tool above. WebM is already selected, so processing starts with the right settings. When it is done, click Download.
If the MKV file already contains compatible streams they are copied without any loss. Otherwise the video is re-encoded at high quality, and the difference is very hard to see.
No. The MKV to WebM conversion runs entirely in your browser using ffmpeg compiled to WebAssembly. Your video never leaves your device.
If the streams can be copied, a few seconds. If the video has to be re-encoded, roughly one to three minutes per minute of 720p video on a computer, and longer on phones.