Video format
What is a .mkv file?
MKV (Matroska) is an open video container that can hold almost any codec, with several audio tracks, subtitles and chapters in one file.
It suits films and series. Browsers and many TVs handle it poorly, so MKV is often remuxed to MP4 for playback.
fileclay opens and writes MKV
MKV vs MP4 vs WebM
| MKV | MP4 | WebM | |
|---|---|---|---|
| Codecs | Almost any | Most modern ones | VP8, VP9, AV1 |
| Subtitles | Full tracks | Basic | Basic |
| Chapters | Yes | Limited | Yes |
| Browsers | Limited | All | All modern |
| Best for | Films with many tracks | Sharing and the web | Video on the web |
When to use MKV
Good for
- Films with several languages and subtitles
- Keeping a recording exactly as captured
- Archiving video
Not a good fit
- Publishing on a website
- Playing on devices that only read MP4
- Editors that don’t import it
How to open .mkv files
| Platform | App | Notes |
|---|---|---|
| Any system | VLC, mpv | Plays nearly every codec |
| Windows | Media Player | Depends on the codec |
| macOS | IINA, VLC | QuickTime doesn’t open it |
| Android | VLC, MX Player | Free apps |
Convert MKV files
From MKV
All 46 output formats: .mp4, .webm, .avi, .mov, .gif, .m4v, .mpeg, .mpg, .ts, .m2ts, .mts, .m2v, .mxf, .ogv, .flv, .vob, .wmv, .asf, .divx, .3gp, .3g2, .ivf, .mp3, .wav, .m4a, .m4b, .ogg, .oga, .opus, .aac, .flac, .aiff, .aif, .wma, .ac3, .mka, .caf, .au, .tta, .wv, .mp2, .png, .jpg, .jpeg, .webp, .bmp
Conversions run in your browser. Files aren’t uploaded.
How to identify a .mkv file
MKV uses EBML, a binary format with this start. WebM shares it, because it’s a subset of Matroska.
It’s read here, in your browser. Only the first bytes.
Your file
What comes after
Questions about MKV
Is MKV better than MP4?
It holds more tracks and codecs. MP4 plays in more places.
Does converting MKV to MP4 lose quality?
Not if the codecs fit MP4 and the tracks are only copied.
Why won’t my TV play MKV?
It may not read the codec or the audio track inside.
Does MKV keep subtitles?
Yes, as separate tracks you can turn on and off.