What Is an MKV File?

How to Open, Edit and Convert Matroska Video Files

Screenshot of several MKV files in Windows 10

file with the .MKV file extension is a Matroska Video file. It's a video container much like MOV and AVI, but also supports an unlimited number of audio, picture and subtitle tracks (like SRT or USF).

This format is often seen as the carrier for high-definition online video because it supports descriptions, ratings, cover art and even chapter points—which is why MKV was chosen as the default video container format for the popular DivX Plus software.

How to Play MKV Files

Opening MKV files might sound like an easy task—just double-click it, like any other video file—but if you have a collection of 10 videos you got from 10 different places, you'll likely find that at least a few of those videos won't play correctly. This problem arises because the correct codecs for that particular type of video must already be present on your computer before the video stream will render. (More about codecs, below.)

Your best bet for playing most MKV files is to use VLC. If you're on Windows, some other MKV players include MPV, MPC-HC, KMPlayer, DivX Player, MKV File Player or The Core Media Player.

Some of those applications will open an MKV file on macOS, too, as can Elmedia Player. Though not free, Roxio software can be used to play MKV files on macOS as well.

On Linux, open MKV files using xine and some of the programs above that work with Windows and Mac, like VLC.

Play MKV files on iPhones, iPads and iPods with the free PlayerXtreme Media Player or VLC for Mobile apps. VLC works with Android devices as well, as does Simple MP4 Video Player (it's named as such because MP4s and other video formats are supported).

Use the CorePlayer mobile software to open MKV files on Palm, Symbian, Windows Mobile and BlackBerry devices. However, the software is not free.

Since you might need different programs to open different MKV files, see How to Change the Default Program for a Specific File Extension in Windows. This step becomes necessary if, for example, KMPlayer is trying to open an MKV file that you instead want or need to use with DivX Player.

Decoder Filters

The Matroska.org website presents a list of decoder filters that must be installed for certain MKV files to play on your computer (in the Additional playback Information section). For example, if the video is compressed with DivX Video, you must install either the DivX codec or FFDshow.

How to Convert an MKV File

A free video file converter is the easiest way to convert an MKV file to a different video format. Since videos files are usually pretty large, an online MKV converter like Convert.Files probably shouldn't be your first choice.

Instead, use a program like Freemake Video Converter to convert the MKV to MP4, AVI, MOV, or even straight to a DVD so you can burn the MKV file with little effort or knowledge of movie burning. Freemake Video Converter is also useful if you want to copy a DVD to the MKV format.

How to Edit MKV Files

As with any other video type, you can add new subtitles to an MKV video or even remove them, plus make custom chapters for the video. Try editing with the free entry-level MKVToolNix program for Windows, Linux and macOS.

Supported subtitle formats include SRT, PGS/SUP, VobSub and SSA. You can delete subtitles that are soft-coded into the MKV file or even add your own custom subtitles. The Chapter Editor portion of the program lets you make start and end times for custom video chapters.

If you're not using the GUI version of MKVToolNix, this command can remove the subtitles:

mkvmerge --no-subtitles input.mkv -o output.mkv

For other tips or help using MKVToolNix, see the online documentation.

To edit the length of an MKV file, cut out portions of the video or merge several MKV videos together, use the Freemake Video Converter program mentioned above.

The MKV Format and Its Codecs

Because the MKV file format is just a general container format, it can hold several different tracks that each use different compression formats. Accordingly, it's not so easy to depend on a single MKV player that can open every MKV file you have.

Certain decoders are necessary for certain encoding schemes, which is why some MKV files may work on one computer but not another—the program that reads the MKV file must load the appropriate decoders. Check out the list of decoders on the Matroska.org website.

Files in the MKA format are just Matroska-related audio, without video. Matroska 3D Vide) files are used for stereoscopic video and Matroska Elementary Stream files just hold subtitles.These formats present with the MK3D and MKS file extensions, respectively.

The Matroska project is supported by a non-profit organization and is a fork of the Multimedia Container Format. It was first announced to the public at the end of 2002 and is a completely royalty-free open standard that's free for both private and commercial use.