Convert MP4 to Matroska (MKV)
Free online converter for MP4 files. Flexible container for high-quality video. Nothing to install, no watermark, and every file is deleted automatically.
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Upload a MP4 file to convert it to Matroska (MKV). Up to 3 files at once, 100 MB each.
Free · up to 3 files · 100 MB each · files deleted automatically after 1 hour.
About MP4 and MKV
MP4 .mp4
The universal video container, normally holding H.264 video and AAC audio. If a device plays video at all, it plays MP4.
Good for
- Plays on effectively every device, browser and editor
- Excellent compression at high quality
- Streams well, and seeks quickly
Trade-offs
- H.264 carries patent licensing obligations
- Lossy — quality drops each time it is re-encoded
- Less flexible than MKV for subtitles and multiple tracks
video/mp4
Matroska (MKV) .mkv
Matroska: an open container that will hold almost any combination of video, audio, subtitle and chapter tracks in one file.
Good for
- Unlimited tracks — multiple languages, subtitles, chapters
- Codec-agnostic, so it holds nearly anything
- Open, well documented, and resilient to damage
Trade-offs
- Browsers will not play it natively
- Many TVs and phones refuse it — the usual reason to convert
- Being a container, contents vary wildly file to file
video/x-matroska
MP4 and MKV side by side
| MP4 | MKV | |
|---|---|---|
| Compression | Lossy (usually H.264) | Container — any codec |
| Transparency | No | Depends on codec |
| Typically used for | Everything — the safe default for video | Archival video, multi-language releases |
What changes when you convert MP4 to MKV
MP4 and MKV are unrelated containers
MP4 is built on the ISO base media format, derived from QuickTime. MKV is Matroska, an open container that accepts almost any codec. A container is a box, not a compression method: what decides how a video looks and how large it is, is the codec stored inside, and these two boxes accept different ones.
This is a re-encode, not a repackage
Some tools can move a stream into a different container untouched when the codecs happen to line up. We do not — every job here is decoded and encoded again, so the conversion takes time in proportion to the length of the file and costs a small amount of quality even where a repackage would have been possible. In exchange the output is predictable: it plays everywhere, rather than inheriting whatever the source happened to contain.
What your MKV will contain
The output is H.264 video with AAC audio — Matroska imposes no codec restrictions, so the choice here is for compatibility rather than because the container demands it. What Matroska adds is room — multiple audio tracks, subtitles and chapters all have a proper place in it, which is why it is the format of choice for archiving a film.
Other MP4 conversions
Other ways to get Matroska (MKV)
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