To convert MP4 to MP3, drop the video above, keep 192 kb/s or pick another bitrate, and press Convert to MP3. The page decodes the sound track in your browser, encodes it with the LAME MP3 encoder and gives you an .mp3 file to download. The video is never uploaded, and a video whose sound is already MP3 is copied without re-encoding.
How to convert MP4 to MP3 online
- Add the video. Drop one or more files on the box above, or press Choose MP4 files. MOV, MKV and WebM videos work the same way.
- Check the sound track. The page lists each sound track with its format, sample rate, channels, duration and language. When a video has several tracks, for example two languages, pick the one you want.
- Choose the bitrate. 192 kb/s suits music; 128 kb/s is plenty for speech. Tick Mono for a voice recording: at the same bitrate, every bit goes to a single channel.
- Press Convert to MP3. A progress bar follows the conversion, then a download link appears with the size and duration of the MP3. In Chrome and Edge on a computer, a result larger than 200 MB is written straight to a file you choose.
What happens to your file
An MP4 is a container: a box holding a video stream, one or more sound streams and the timing that keeps them together. To make an MP3, the page opens the box, reads only the chosen sound stream, decodes it to plain audio samples and encodes those samples as MP3. The picture is never decoded, which is why the conversion takes far less time than playing the video.
All of this runs in your browser. The file is read from your disk in small pieces by a background worker, the sound is decoded by the browser's own audio decoder (WebCodecs), and the MP3 is encoded by LAME 3.100, the encoder behind most MP3 software, compiled to WebAssembly. Nothing leaves your device: there is no upload, no queue and no copy of your recording on a server.
When the sound inside the video is already MP3, which happens with some older MP4 and MKV files, re-encoding would only lose quality. The page then copies the MP3 frames as they are; untick Copy MP3 sound as it is to re-encode at the bitrate you chose.
Which MP3 bitrate to choose
| Bitrate | Size per minute | Good for |
|---|---|---|
| 96 kb/s | 0.7 MB | Voice notes, lectures, mono speech |
| 128 kb/s | 0.96 MB | Podcasts, interviews, audiobooks |
| 192 kb/s | 1.44 MB | Music and mixed content: the default |
| 256 kb/s | 1.92 MB | Music from a high-quality source |
| 320 kb/s | 2.4 MB | The MP3 maximum, for archiving music |
The MP3 is encoded at a constant bitrate, so the size is the bitrate multiplied by the duration, and every player shows the right length. A higher bitrate cannot bring back detail that the source never had: the sound of a phone video or a 128 kb/s stream gains nothing above 192 kb/s.
MOV, MKV and WebM to MP3
The same box converts MOV to MP3 (iPhone and QuickTime recordings), MKV to MP3 (films, series and OBS recordings) and WebM to MP3 (screen recordings and browser captures). It also takes audio files: M4A, AAC, Ogg, Opus, WAV and FLAC become MP3 the same way.
What matters is the sound format inside the file, not the file extension:
- AAC, Opus, Vorbis and FLAC are decoded by the browser's WebCodecs audio decoder, available in Chrome and Edge and in recent versions of other browsers. PCM (WAV, some MOV files) is read directly by the page.
- MP3 is copied without re-encoding, which works in every browser.
- AC-3, E-AC-3 and DTS (surround sound from TV recordings and films) are often missing from browser decoders. The page checks before converting; when your browser cannot decode the track, it says so and shows the ffmpeg command that converts it.
Surround sound (5.1 or 7.1) is mixed down to stereo, since MP3 holds two channels at most. MP3 accepts sample rates up to 48 kHz; a 96 kHz track is refused with a command that resamples it.
MP3 or another audio format?
MP3 plays on every phone, car stereo, smart speaker and old MP3 player, which is why it stays the default choice. Two other formats are worth knowing:
- M4A keeps the AAC sound of an MP4 without any conversion, so it loses nothing and takes a second. With ffmpeg:
ffmpeg -i video.mp4 -vn -c:a copy audio.m4a. Most modern players read M4A. - WAV stores the decoded sound uncompressed, for audio editors, DAWs and transcription software that expect it. The MP4 to WAV converter does that in the browser, with the same file handling as this page.
Other ways to convert MP4 to MP3
ffmpeg
Free on Windows, macOS and Linux, and the fastest way to convert a whole folder. The page shows the command for each file under Same conversion with ffmpeg; the general form is:
ffmpeg -i video.mp4 -vn -c:a libmp3lame -b:a 192k audio.mp3-vn drops the picture, -c:a libmp3lame selects the LAME encoder and -b:a 192k sets the bitrate. To keep an MP3 track as it is, replace the last two options with -c:a copy.
VLC
In VLC, open Media, Convert / Save, add the MP4 and press Convert / Save. Choose the profile Audio - MP3, give a destination file ending in .mp3 and press Start. VLC converts one file at a time and shows its progress on the time slider.
Online converters that upload
Sites such as CloudConvert and FreeConvert send your video to their servers, convert it there and let you download the MP3. That means uploading the whole video, picture included, for a sound track that is often a tenth of its size, a size limit on free plans, and a copy of your file on someone else's server.
Limits
- Memory. Without writing straight to disk, the MP3 is assembled in memory: up to 1 GB on a computer and 300 MB on a phone or tablet, which is almost 7 hours at 320 kb/s on a computer. Chrome and Edge on a computer write results above 200 MB straight to disk.
- Browser decoders. The sound is decoded by your browser, so a format it does not support (often AC-3, E-AC-3 and DTS) cannot be converted here; the ffmpeg command takes over.
- MPEG-TS and protected files. .ts recordings are not read by this page: remux the .ts recording into an MP4 first, without re-encoding. Files protected by DRM, such as purchased films, cannot be converted.
- One track per MP3. Each conversion takes one sound track. Convert the file again with another track selected to get the second language.