# MP4 to MP3 Converter - Extract Audio, Free

Page: https://hirantha.me/tools/mp4-to-mp3
Part of: Hirantha Sandaruwan Lakshan free tools (https://hirantha.me/tools)
Updated: 2026-07-31

Extract the audio from a video file as an MP3.

This is a free tool that runs in the browser: open the page to use it. File tools process files on the visitor's own device; files are never uploaded or stored. No account, sign-up, payment or watermark.

Pull the audio track out of an MP4 video and save it as an MP3, entirely in your browser. Trim to just the section you need before extracting, or keep the whole thing.

The video's audio track is read directly and re-encoded to MP3 through a real LAME encoder running as WebAssembly - the video track itself is discarded rather than decoded, which is what keeps this fast.

The tool never fully decodes the video to extract audio - it streams through the file's encoded packets directly, which keeps memory use low even for a long recording.

Set an in-point and out-point before extracting if you only need a section, like the music from part of a longer video.

Q: Is my video uploaded anywhere?
A: No, the whole process runs in your browser tab.

Q: Can I trim before extracting the audio?
A: Yes, set an in and out point and only that section is extracted.

Q: Does it keep the video quality info or just audio?
A: Only audio - the output is a standard MP3 file with no video track.

Q: Is there a file size limit?
A: There's a soft warning on very large files on mobile, but no hard cap - it depends on your device's memory.

Q: What bitrate is the extracted MP3?
A: The audio is re-encoded at a bitrate chosen to stay transparent for speech and music without inflating the file. For most source videos the result is indistinguishable from the original track.

Q: What if the video has no sound?
A: There's nothing to extract, and the tool says so rather than handing you a silent file.

Q: Does this work with MOV, MKV, or WebM too?
A: Yes. Any video your browser can decode works the same way, not just MP4.

Q: Why does a long video take a while?
A: The audio track still has to be decoded and re-encoded end to end. It's much faster than re-encoding video, but it isn't instant on a feature-length file.

Q: Does this work on my phone?
A: Yes - it runs in your phone's browser with no app to install. A very long video is more likely to run into memory limits on a phone than on a laptop.

Sources: MP3 (MPEG-1 Audio Layer III) (https://en.wikipedia.org/wiki/MP3); WebCodecs API - MDN (https://developer.mozilla.org/en-US/docs/Web/API/WebCodecs_API)

Related tools:

- [Audio trimmer](https://hirantha.me/tools/audio.md): Cut a section from an audio file and convert it to MP3, M4A, or WAV.
- [Video compressor](https://hirantha.me/tools/video.md): Shrink a video so it's small enough to email or message.