What is an MKV file?
By Ajiri Ogba · Updated
MKV is the Matroska video format: an open, free container that can hold video plus any number of audio tracks, subtitle tracks and chapters in a single file. It's popular for recordings and archived video, but many phones, TVs and editing apps only play MP4, so MKV is often converted.
What makes MKV different
- Several audio languages and subtitle tracks in one file
- Chapters and attachments such as fonts
- Almost any video or audio codec
- Open and royalty-free (WebM is based on a subset of Matroska)
What happens when you convert MKV to MP4
MP4 supports fewer kinds of tracks. This site's MKV converters keep one video and one audio track — ffmpeg's default choice: the highest-resolution video and the audio track with the most channels — and re-encode them as H.264 and AAC. Extra audio languages aren't carried over, and image-based subtitles (PGS/VobSub) can't be stored in MP4.
To keep specific tracks, or to rewrap an MKV that already has H.264 and AAC without re-encoding, use desktop ffmpeg with -map and -c copy.