How to Open and Play MKV Files

MKV (Matroska Video) is a container format, not a codec. One MKV file can hold a video stream, several audio tracks, multiple subtitle tracks and chapter markers. Whether a player can open the file depends on two things: whether it understands the Matroska container, and whether it can decode the specific video and audio codecs stored inside.

Before you start

Make sure the file finished downloading or copying. A partial file may refuse to open, stop partway through or fail when you seek. Note your operating system and its version, because built-in support for MKV differs between platforms and releases.

Decide whether you want local playback or an online service. A desktop or mobile media player decodes the file on your own device. A web-based MKV viewer or converter usually requires uploading the file first. Before uploading personal recordings or private calls, read the service's terms on storage, retention and deletion. Do not assume a file is deleted after processing unless the provider states it.

If you can, find out which codecs the file uses. Many players show this in a media information or codec information window, and dedicated media info tools display it as well. Common video codecs in MKV files are H.264, HEVC (H.265), VP9 and AV1. Common audio codecs are AAC, AC-3, DTS, FLAC and Opus. Most cases where an MKV file won't play come from an unsupported codec rather than from the MKV format itself.

Step-by-step instructions

Choose a player for MKV

Free cross-platform players with their own built-in decoders, such as VLC media player and mpv, play MKV files on Windows, macOS and Linux. VLC is also available for Android and iOS. Built-in apps vary. Recent Windows media apps can open MKV files, but some codecs, HEVC in particular, may require an additional extension from the Microsoft Store. QuickTime Player on macOS does not open MKV files natively, so Mac users normally install a third-party player.

Open the file

• 1. Install the player from the developer's official website or your platform's app store. Avoid bundled installers from unknown download sites.
• 2. Start the player and use its open file command, or drag the MKV file onto the player window.
• 3. Alternatively, right-click the file in your file manager, choose Open with, and select the player.
• 4. If you want MKV files to open in this player every time, set it as the default app through the Open with dialog or your system's default apps settings. You can change this back later in the same place.

Select audio and subtitle tracks

An MKV file may contain several audio languages, a commentary track or multiple subtitle tracks. Full-featured players let you switch audio and subtitle tracks while the video plays, usually from a menu or a right-click menu. The exact names and locations differ by player and version. If your subtitles are in a separate file, such as SRT or ASS, many players load them automatically when that file has the same name as the video and sits in the same folder. Otherwise, load the subtitle file manually.

Phones and tablets

On Android, some built-in video and gallery apps play MKV files, depending on the device and the codecs in the file. On iPhone and iPad, the built-in apps generally do not play MKV, so install a third-party player and open the file from the Files app or through the player's own import option.

Check the output

Play the beginning, the middle and the end of the file, and jump between points rather than watching only the first few seconds. Problems with seeking, audio sync or late subtitle tracks often appear only further into the file.

• Picture: video moves smoothly, with no green or black frames and no stretched aspect ratio.
• Sound: the expected language track plays, at the right volume, in sync with the picture.
• Subtitles: the chosen track appears, displays correct characters and is correctly timed.
• Navigation: seeking works, and chapters are listed if the file contains them.

A player does not change the quality of the file. It can only show what the file contains. Whether high-resolution HEVC or AV1 video plays smoothly depends on your device's decoding capability. HDR content may look dull or washed out on a non-HDR display, depending on how the player converts it.

Common problems and next steps

Video plays but there is no sound

Two causes are most likely. Either the selected audio track uses a codec the player cannot decode (DTS, AC-3 and TrueHD are common examples in some built-in apps), or the player is set to pass audio through to a device that cannot decode it. Switch to another audio track, check that the correct output device is selected, or use a player with broader codec support.

Sound plays but the picture is black, green or missing

The video codec is probably unsupported, or hardware-accelerated decoding is failing. Try turning off hardware decoding in the player's settings, updating your graphics driver, or installing the platform's official codec extension. Do not install codec packs from unknown sources.

The file will not open at all

Try a second player. If the file fails in several players, it is probably incomplete or damaged, so download or copy it again from the original source. Also check that the file really is an MKV, because a renamed extension can confuse some apps.

Subtitles are missing or show wrong characters

First confirm that a subtitle track is turned on. If an external subtitle file shows garbled text, the file is probably not encoded in UTF-8. Change the subtitle encoding in the player's settings, or save the subtitle file as UTF-8. Styled ASS subtitles may look different from one player to another.

A TV, phone or editing app does not accept MKV

If the codecs inside are supported by the target device, you can remux the file into MP4 without re-encoding. FFmpeg, for example, can copy streams into a new container. Remuxing keeps the original quality, but MP4 does not carry every subtitle format that MKV does. If the codecs themselves are unsupported, the file has to be converted (re-encoded). This takes longer and can lower quality. In either case, keep the original MKV until you have checked the new file.