What is a .mkv file?
Matroska Video · Video · Matroska (open source) · 2002
MKV is a flexible open container that can hold almost any video, plus many audio tracks, subtitles and chapters in one file. It is popular for high-quality movies and archives, though it is not natively supported in most browsers.
What is a .mkv file used for?
Matroska can wrap essentially any codec and pack in multiple audio languages, several subtitle tracks and chapter markers, which makes it the format of choice for full movie files.
That flexibility is also why browsers and some devices do not play MKV directly. The desktop player VLC handles it effortlessly.
To play an MKV on a phone or in a browser, converting to MP4 is the usual fix.
How to open a .mkv file
The .mkv format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .mkv file.
Windows
- VLC
- MPC-HC
- Media Player (Windows 11)
macOS
- VLC
- IINA
- mpv
Linux
- VLC
- mpv
Web
- Not natively, convert to MP4 or WebM
How to convert a .mkv file
You can convert a .mkv file to MP4, WebM, MOV using a conversion tool or the export menu of an app that opens it.
.mkv file signature (magic bytes)
Programs recognise a .mkv file by the bytes at the start of the file, not by its name. These are the signatures for MKV. For a full breakdown, see the MKV file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 1A 45 DF A3 | 0 | EBML header (Matroska/WebM) |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .mkv file?
MKV is a flexible open container that can hold almost any video, plus many audio tracks, subtitles and chapters in one file. It is popular for high-quality movies and archives, though it is not natively supported in most browsers.
Why won't my MKV play on my phone or browser?
MKV is not natively supported by most browsers and many phones. Play it in VLC, or convert it to MP4.