Convert MP4 to MKV, keeping every stream without quality loss when possible. Free and private 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 MP4 video onto the page, paste it, or click to choose. It is read directly from your device.
Everything is set up for MKV. 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 MKV file to your device.
MPEG-4 Part 14
The universal video format
MP4 is the most widely used video format, usually with H.264 video and AAC audio. Phones, cameras, websites and social networks all use it.
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.
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 MP4 file to the tool above. MKV is already selected, so processing starts with the right settings. When it is done, click Download.
MKV accepts almost any codec, so the streams are usually copied exactly as they are — no quality is lost and conversion takes seconds.
No. The MP4 to MKV 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.