What is an MKV file?
MKV is the Matroska container, an open format from 2002 that can hold practically any video and audio codec together with multiple audio tracks, subtitles, chapters, and attachments. Its design tolerates interruptions, which is why OBS and other recorders write MKV: a crash mid-recording leaves a playable file, unlike MP4. Media collectors like it because one file carries every language and subtitle track.
Where MKV fails
Phones, smart TVs, game consoles, web upload forms, and most editing software either reject MKV or handle it badly. The video inside is usually H.264 with AAC audio, so converting to MP4 is a container swap that takes seconds and loses nothing. Extra audio tracks and subtitle tracks are dropped in the process; the first audio track is kept.
Converting OBS recordings
OBS can remux to MP4 itself under File, Remux Recordings, but if you only have the MKV, our converter does the same in the browser. For sharing, follow up with the video compressor to bring a long recording down to a manageable size.
Frequently asked questions
Is MKV better than MP4?
MKV is more flexible; MP4 is more compatible. For storage and multi-language libraries, MKV; for sharing and playback anywhere, MP4.
Are subtitles kept when converting MKV to MP4?
No. Subtitle tracks are removed because MP4 players handle them inconsistently. Burn them in with a video editor if you need them.