MKV file format
MKV holds anything you throw at it: several audio tracks, switchable subtitles, chapters and any codec. It is the archivist's container, not the sharing one.
or drag & drop them here · images, video, audio and documents · up to 2 GB
What is MKV?
Matroska appeared in 2002 as a deliberately open, deliberately unlimited container. Where MP4 was designed by a standards body with streaming in mind, MKV was designed by a community that wanted one file to hold an entire disc: the film, the original and dubbed audio, half a dozen subtitle languages, chapter markers and cover art, all switchable during playback.
That flexibility is why film collections live in MKV. It is also why compatibility is uneven. Because MKV imposes no restrictions on codecs, a player must support both the container and whatever is inside it, and most smart TVs, consoles and phone apps support only a narrow slice. The file is fine; the device simply does not know how to read it.
The useful thing to know is that MKV and MP4 share most codecs, so converting between them is usually a remux rather than a re-encode: the streams are copied into a new container untouched, which takes seconds and loses nothing. Quality is only lost if the audio or video actually needs re-encoding for the target device.
| Extension | .mkv |
|---|---|
| Category | Video |
| MIME type | video/x-matroska |
| Released | 2002 |
| Developed by | Matroska / CoreCodec |
| Compression | Container (depends on codec) |
MKV: frequently asked questions
- Why do movie files so often come as MKV?
- Because it is the only common container that holds everything a disc has: multiple audio languages, several subtitle tracks, chapters and high-bitrate video, all in one file. Nothing has to be thrown away or split out, which makes it the natural choice for archiving.
- Why will my TV not play MKV files?
- Most TVs and media players support a fixed list of containers and codecs, and MKV is often outside it — or the container is supported but the video inside is not. Converting to MP4 with H.264 video is the reliable fix for living-room hardware.
- Does converting MKV to MP4 lose quality?
- Not if the streams are simply copied across, which is possible whenever the codecs are already MP4-compatible. That is a remux: fast and completely lossless. Quality is only affected when the video genuinely has to be re-encoded for the target device.
- What happens to subtitles when I convert MKV to MP4?
- MKV usually carries soft subtitles — separate switchable tracks. MP4 supports them poorly, so most conversions drop them or leave them invisible. Extract the subtitle track to an .srt file first, or burn it into the picture if it must always be visible.
- My MKV has several audio tracks — which one survives?
- Typically only the first. Converters default to the first audio stream unless told otherwise, so a film with English and dubbed tracks can silently come out in the wrong language. Check which track is which before converting if the file is multilingual.
- MKV or MP4 — which should I use?
- MKV to store and archive, MP4 to share and play. Keep the MKV as your master with everything intact, and produce an MP4 whenever a specific device, platform or person needs the video in a form that is guaranteed to open.