Convert images, documents, video and audio in your browser. Your files stay on your device.
Convert WEBM videos to MKV right in your browser, using your device’s hardware acceleration when available. You can also trim, resize or remove the audio.
Drag one or more WEBM files onto the dashed area, or tap it to pick them from your device.
MKV is already selected. If you want, open the options to trim the video or change its resolution or quality.
Press “Convert to MKV”. When it’s done, download the files one by one or all together in a ZIP archive.
Good to know. If the video is already compatible with the chosen format it’s copied without re-encoding: the conversion is very fast and the quality identical.
Source format
WebM (a Google project)
Born for the web, it uses only open, royalty-free codecs. It’s the format many browsers use to record the screen and webcam. Outside the browser, though, it doesn’t always open.
Target format
Matroska Video
An open, flexible container that accepts almost any codec, several audio tracks and subtitles. It’s loved for films and series, but TVs, iPhones and some editors can’t read it.
Audio and video use WebCodecs: they work in up-to-date Chrome, Edge, Opera and Samsung Internet, in Firefox 130+ and Safari 17+ (with a few limits on the formats they can create). If your browser can’t create the chosen format, we tell you before you start.
No. The conversion from WEBM to MKV happens entirely in your browser, using your device’s computing power. Files aren’t sent or stored anywhere: when you close the page they’re gone from memory too.
Up to 100 files at a time. There’s no fixed size limit: it depends on your device’s memory. On smartphones it’s best to work in smaller batches with heavy files such as videos.
Yes, with up-to-date Safari, Chrome, Firefox, Edge and Samsung Internet. On phones, converted files end up in the Downloads folder or the Files app.
Only to open the page (and, the first time, to download the components needed for that type of file). After that the conversion keeps working even if the connection drops.