# Convert MKV to MP3

> Convert MKV to MP3 online free: OBS recordings and downloads lose the picture and keep the sound as MP3 up to 320 kbps. Batch, no upload. No sign-up.

URL: https://nibbo.org/en/mkv-to-mp3/

## MKV

MKV (Matroska) is the container of OBS Studio recordings, many downloads and rips. It can hold almost any codec, plus several sound tracks and subtitles.

OBS records H.264 with AAC unless set otherwise, which fits MP4 as it is. Phones, iMovie, Premiere and most social networks don’t open MKV, which is why it so often becomes MP4.

## MKV to MP3: remux or re-encode

Only the soundtrack of the MKV is decoded; the picture is never touched. The sound is encoded with LAME, the reference MP3 encoder, at 128–320 kbps.

An MP3 is far smaller than the video: a minute at 192 kbps is about 1.4 MB, so an hour-long recording becomes roughly 85 MB.

## How it works

1. Drop one or more MKV files: MP3 is already selected. Quality, maximum resolution and sound can be changed before you start.
2. The soundtrack is decoded by your browser, or by FFmpeg compiled to WebAssembly for formats it can’t open, and saved as MP3.
3. Download each file, or all of them as one ZIP.

## Questions

### Are subtitles and extra sound tracks kept?

The first video and the first sound track are converted. Subtitles and other tracks stay in the MKV.

### Are my videos uploaded?

No. Reading, remuxing and encoding all run in this browser tab. Open DevTools and watch the Network tab while a file converts: no request carries it.

### Why is one file done in seconds and another takes minutes?

A remux only copies the streams, so it runs at disk speed. A re-encode decodes and encodes every frame; FFmpeg in WebAssembly, used when the browser can’t, is slower still.

### How large can a video be?

Up to 3 GB per file for free, and as many files as you like. Remuxes and WebCodecs re-encodes stream from the disk; the FFmpeg path holds the result in memory.

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