Convert MKV to MP3
Pull the sound out of Matroska videos as MP3s that play anywhere, on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No sign-up, no watermark. The limit is your device’s memory (phones hold less).
Extract the audio track from MKV videos as MP3 in your browser. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The limit is your device’s memory, which is smaller on a phone, and after your first run the page works offline.
Your iPhone may take a few seconds to prepare the video first, longer if it's stored in iCloud.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
MKV (Matroska) is a container rather than a codec: one file can hold any video, several audio tracks, subtitles and chapters. OBS recordings, screen captures, game clips, anime and a lot of downloaded video come as MKV. Getting an MP3 out of one is useful for a talk you want to listen to on a walk, the music from a recorded set, or dialogue to send to a transcription service.
Whether a browser can read the sound depends on what codec sits inside the MKV. Opus, Vorbis, FLAC and MP3 tracks decode in every modern browser, and AAC tracks in Chrome, Edge and Safari; this page turns any of them into MP3. Films ripped from Blu-ray or DVD often carry Dolby AC-3, E-AC-3, DTS or TrueHD surround audio instead, which browsers do not decode; for those the page says plainly that no audio could be read, rather than giving you a silent file.
When an MKV has several audio tracks (a second language, or a director’s commentary), the browser reads the first one. Surround tracks are mixed down to stereo, or to mono if you choose it. OBS records microphone and desktop audio into one track by default, which is the track you get here.
The page opens at 192 kbps, a good match for music and film audio. For lectures, meetings and streams of people talking, 96 or 128 kbps in mono is plenty and makes much smaller files.
How it works
- Drop one or more MKV files, or tap to pick them.
- Keep 192 kbps for music, or choose a lower bitrate and mono for speech.
- Convert. The MP3 downloads; several come as a zip.
In your browser, not on a server
Your browser decodes the sound track with the same audio decoders it uses to play media on any website (AAC for MP4, MOV and M4A; Opus or Vorbis for WebM; FLAC, WAV and MP3). The samples are resampled to 44.1 kHz and handed to LAME, the reference MP3 encoder, compiled to WebAssembly and served by this site. WAV files are written directly by a few lines of code in the page. Everything happens in memory in your tab.
Compared with upload-based tools: Online converters upload the whole video just to keep its sound, cap free files at a few hundred megabytes, and make you wait in a queue. Home videos, lectures and voice memos are personal. Here the file never leaves your device, so a 1 GB video converts as fast as your computer can read it, and the limit is your device’s memory (phones hold less).
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Why does my MKV say no audio could be read?
Its sound track probably uses Dolby (AC-3, E-AC-3, TrueHD) or DTS, common in films ripped from discs, which browsers cannot decode. MKVs from OBS, phones, screen recorders and most web sources use AAC or Opus; if an AAC track fails in Firefox, try Chrome or Edge.
My MKV has two languages. Which one do I get?
The first audio track. Picking another track needs a desktop tool such as MKVToolNix or VLC to set it as default or split it out first.
Is there a size limit?
No fixed limit. The whole sound track is decoded in memory, so a two-hour film needs around 2.5 GB of free memory; recordings of an hour or less are comfortable on most computers.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Video to MP3
Pull the sound out of a video, or turn any audio file into an MP3. Your files are converted on this device and never uploaded.
Merge videos
Combine clips into a single video, in the order you choose. Done on this device, never uploaded.
Add audio to video
Put music or a voice-over on a video, or replace its sound. The picture is copied as it is, and nothing is uploaded.
Reverse video
Make a clip play backwards, for a rewind effect, a boomerang or a laugh. Done on this device, never uploaded.
Other conversions
Guides
- How to convert a video to MP3This is different from muting a video: you want the sound saved as its own file. Most devices have no built-in way to do that.
- Is Zamzar safe?Zamzar is one of the oldest online converters. Its storage window is longer than most, which is the detail worth knowing.
- A free CloudConvert alternative for everyday filesCloudConvert measures its free tier in credits tied to conversion time, not files, which makes it hard to predict when you will hit the limit. Here is an alternative with nothing to meter.
- A free Convertio alternative with no file size capConvertio's free plan caps both file size and how many conversions you get per day. Here is an alternative with no such ceiling.
- A free Zamzar alternative with no daily limitZamzar's free service limits how many files you can convert and how big each can be. Here is an alternative with no such cap.