Convert MKV to MP3
Pull the audio track out of an MKV video, whether it's an OBS recording or a rip of your own disc, and save it as a stereo or mono MP3.
Pull the audio track out of an MKV video, whether it's an OBS recording or a rip of your own disc, and save it as a stereo or mono MP3.
Matroska (.mkv) is a flexible container that can hold almost any video and audio codec, several audio tracks, subtitles and chapters in one file. OBS users record to it because an interrupted recording stays playable, and it is a common format for rips of your own discs. That flexibility is also why phones, car systems and many audio apps refuse to open it.
When you convert MKV to MP3 here, the video, subtitles and extra streams are left behind and one audio track is encoded as MP3 at 192 kbps CBR. Mono and stereo sources keep their layout, surround sound is folded down to stereo, and sample rates above 48 kHz are lowered to 48 kHz. There are no options to adjust.
Unlike MP4 or WebM, an MKV doesn't point to one likely codec. What you started with decides how big a change the MP3 represents:
| Source audio | Commonly found in | What conversion does |
|---|---|---|
| AAC stereo | OBS recordings | Lossy re-encode to MP3 |
| AC3 or DTS 5.1 | DVD and Blu-ray rips | Downmix to stereo, then MP3 |
| FLAC or PCM | Music video and concert rips, archival copies | Lossless source becomes lossy MP3 |
| Opus or Vorbis | Files made with open-source encoders | Lossy re-encode to MP3 |
The surround downmix deserves a note. A 5.1 movie track spreads dialogue, music and effects across six channels; the stereo MP3 combines them into left and right. Speech usually stays clear, but you lose any sense of sound coming from behind you. For a FLAC or PCM source, 192 kbps MP3 is a big step down in file size and a small one in fidelity, acceptable for listening but not ideal as your only copy of a high-resolution recording.
Output size depends only on running time: about 1.44 MB per minute. A 5-minute clip becomes roughly a 7.2 MB MP3, whether the source was a lightweight screen capture or a heavy gameplay recording.
MKV files can have several audio tracks: OBS can record up to six, and rips often carry multiple languages or a commentary track. The converter uses FFmpeg's default choice, usually the first or main track, and you can't pick another. If you need a different one, use a tool such as MKVToolNix to save a copy that contains only that track, then upload the copy. In OBS, routing your microphone and game audio to Track 1 ensures both end up in the MP3.
Cut the file to the section you want, or lower the recording bitrate or resolution for future sessions. Remuxing an MKV to another container does not reduce size much, because the video itself is unchanged.
Encrypted or DRM-protected content can't be converted. Only use MKV files you created or have the rights to.
Want to avoid lossy compression for a FLAC or PCM track? The FLAC converter keeps the audio lossless at its original bit depth. The FLAC to MP3 page explains the lossless-to-lossy trade-off in more depth.
| Full name | MPEG-1/2 Audio Layer III |
|---|---|
| Compression | Lossy |
| Developed by | Fraunhofer IIS / MPEG |
| Introduced | 1993 |
| File extension | .mp3 |
| Typically used for | Music libraries, podcasts, everyday listening |
| Plays on | Virtually every phone, computer, browser, car stereo and media player |
| Our output | LAME MP3, 192 kbps CBR, stereo |
The converter uses FFmpeg's default audio track, which is usually the first or main one, and you can't choose another. To convert a different track, use a tool such as MKVToolNix to save a copy of the MKV that contains only the track you want, then upload that copy.
MP3 supports only mono and stereo, so a 5.1 AC3, DTS or similar track is downmixed to two channels. Dialogue and music remain, but the rear and center channel separation is lost. The stereo result is encoded at 192 kbps, which is fine for listening on headphones or speakers.
No. MP3 is a lossy format, so a FLAC or PCM track becomes a compressed copy at 192 kbps. It will sound very close to the original for most listening, but some detail is discarded. Keep the MKV, or convert to FLAC instead, if you need a lossless version.
The most likely reason is size: uploads are limited to 50 MB, and gameplay or camera recordings at high bitrates pass that within a minute or two. Trim the recording to the part you need, or record at a lower bitrate or resolution, then try again.
Yes, if both were recorded to the same track. OBS lets you send each audio source to up to six tracks, and the converter only reads one, usually the first. Make sure your microphone and desktop audio are both assigned to Track 1 before recording.
Need detailed information or want to set a different default format? Visit our specific converter pages: