MKV (Matroska) is a flexible container used by OBS, many downloads and archives. It can hold almost any codec and several sound and subtitle tracks, but phones, iMovie and many TVs won’t open it.
Most MKV files from OBS and the web contain H.264 or HEVC video with AAC or Opus sound. H.264 is moved into MP4 without re-encoding; HEVC and VP9 are re-encoded to H.264 so the MP4 plays everywhere. The video never leaves your device. It is read and saved by your browser, so there is no upload, no queue and no copy on a server.
How to convert MKV to MP4
- Drop your MKV file on the box above.
- MP4 is already selected. You can pick another format if you need one.
- Press Convert to MP4 and download the new file.
Questions
Will I lose the subtitles?
The MP4 gets the main video and sound track. To keep subtitles, pull them out first with the subtitle extractor, which saves them as SRT.
My MKV has several audio tracks. Which one is kept?
The first (default) track.
Is OBS recording to MKV a good idea?
Yes, MKV survives a crash mid-recording. Convert to MP4 afterwards here.