AnyFormat

00 MKV → MP3

MKV to MP3

Handles the multiple audio tracks MKV files usually carry.

Drop files or a folder here

or choose from your device · paste with ⌘V / Ctrl+V

.mkv

03Options 5

Right for speech, wrong for music. At a fixed quality the file size does not change — but mono tolerates a much lower quality than stereo, so combine the two to actually shrink the file.

Leave at 0 for the whole file.

0 means run to the end.

  • No upload The conversion runs in this tab. Your file never travels — not to us, and not to the advertising.
  • No sign-up, no email, no daily cap There is no account system to sign up to.
  • No size limit we invented Only your device's memory — about ~2 GB on a desktop browser, ~400 MB on a phone.
  • Turn your Wi-Fi off and convert anyway The conversion needs nothing but this page. Ads will not load without a connection; your file will still convert. That is the whole claim, and it takes five seconds to check.

Extracts audio from a Matroska file. MKV is the container of choice for archival video precisely because it holds anything — which means an MKV is more likely than most to have several audio tracks in it.

Multiple audio tracks

MKV files routinely carry several: the original language, a dub, a director's commentary, sometimes an audio-description track. The first is converted and you are told how many there were.

If the first is not the one you want, there is no way to pick another here yet. A desktop tool such as MKVToolNix can extract a specific track without re-encoding, which is also faster.

Surround sound tracks usually fail, and here is why

Many MKV files carry AC-3, E-AC-3 or DTS surround audio. No browser decodes any of them — they are patent-encumbered and have never been included.

When that is what your file has, you are told which codec it is rather than getting a bare failure. The workaround is a desktop tool. If the file also has a stereo AAC track, that one converts fine.

Formats a browser genuinely cannot read

The decoding here is the browser's own, which is fast and needs no download — and which has real gaps.

WMA (Windows Media Audio), AC-3 and DTS (cinema surround tracks), AMR (old phone voice recordings) and RealAudio are not decodable by any browser. If your file uses one you are told which, rather than being left with a failure that says nothing.

HEVC video cannot be decoded either — but that does not matter here. Extracting audio discards the video track before anything tries to decode it, so an iPhone recording converts perfectly well even though the browser could not play its picture.

How MP3 encoding works without a server

Browsers decode MP3 but do not encode it — there is no MP3 encoder in WebCodecs. The encoding here is LAME, the reference open-source MP3 encoder, compiled to WebAssembly and loaded only when you actually convert to MP3.

It is the same encoder desktop software has used for twenty years, producing standard files that play everywhere. Because it is fetched on demand, pages that convert to WAV or M4A never download it.

Other names for this

Also searched as “matroska to mp3”, “extract audio from mkv”.

Questions

It says the audio codec cannot be decoded.
The track is probably AC-3 or DTS surround, which no browser decodes. If the file has a stereo AAC track as well, that one works.
Can I choose which audio track to extract?
Not yet — the first is used, and the count is reported. MKVToolNix can extract a specific track without re-encoding.
Is my file uploaded?
No. The demuxing, decoding and encoding all happen in this tab using the browser’s own media stack plus a WebAssembly encoder. A recording can be an interview, a lecture, a private call — none of it is transmitted. Turn your Wi-Fi off after the page loads and it still works.
How large a file can I convert?
There is no imposed limit, only your device’s memory — around 2 GB in a desktop browser and 400 MB on a phone, since the file is held in memory while it converts. A two-hour video converts in well under a minute on a laptop.
Can I convert several files at once?
Yes. Drop as many as you like, or a whole folder. Each keeps its original name with the new extension, and you can download them individually or as a ZIP.