Turn MP4 files into MKV
Convert an MP4 into an MKV right here on the page. MKV keeps a whole release in one file: the picture, several audio languages, subtitles and chapters. Worth knowing: an MKV will not open in a browser tab, so it is a file for software rather than for the web. Your file never leaves your computer.
Need the other direction? Convert MKV to MP4
How to convert MP4 to MKV
- 1 Drop your MP4 .mp4 file onto the page, or click to browse for it.
- 2 Set the quality, or leave the default, which keeps the file small without anything showing.
- 3 Convert. The work happens on your own machine, so how long it takes depends on your computer and the file.
- 4 Download the MKV, or add more files and do the whole set in one go.
Why convert MP4 to MKV
- Holds unlimited audio, subtitle, chapter and attachment tracks.
- Holds almost anything, and it is an open format still being maintained.
- Film and series releases with multiple languages and subtitles.
- MP4: fussy about subtitle tracks and unusual audio tracks.
MP4 compared with MKV
How the two formats differ on the things that decide whether a conversion is worth making.
| Property | MP4 | MKV |
|---|---|---|
| File extension | .mp4 | .mkv |
| Compression | Lossy | Lossy or lossless |
| Typical file size | Smaller | Depends on mode |
| Browser support | Every browser | No browser support |
| Introduced | 2001 | 2002 |
| Developed by | ISO/IEC MPEG | Matroska community |
Quality and what changes
MKV stores the same content under a different set of rules, so what matters here is compatibility rather than picture quality. Convert once from the best source you have rather than through a chain of intermediate files.
- Browsers will not display an MKV, so it downloads rather than opening in a tab.
- One MKV limitation to keep in mind: cannot be streamed on a web page without repackaging it first.
Questions about MP4 to MKV
Can I open an MKV in a browser?
No. No mainstream browser renders MKV natively, so it will download rather than display. That is fine when the file is heading into desktop software or an archive, and a problem if it is going on a web page.
Is my MP4 file uploaded anywhere?
No. The whole thing runs inside the browser tab you already have open. Your MP4 is read straight from your own disk, converted on your machine and handed back as an MKV. Nothing is sent anywhere, nothing is stored and there is no account.
Is there a file size limit?
There is no server-side limit because no server sees the file. The real ceiling is your device memory, since the input and the output both have to fit in the tab. A few hundred megabytes is usually fine on a desktop machine and considerably less on a phone.
Can I convert several MP4 files at once?
Yes. Add as many as you like and they are processed one after another, then offered as separate MKV downloads or as a single ZIP. Speed depends on your own processor rather than on a queue.
Does the converter work offline?
Yes, after the page has loaded once. The engine is cached by the browser, so you can disconnect, reload and keep converting. That falls out of doing the work locally rather than being a separate mode you switch on.