Audio Converter
ffmpeg.wasm encodes to MP3 with the LAME encoder inside your browser.
How Audio Converter works
Convert WAV, M4A or OGG audio into MP3. ffmpeg.wasm encodes to MP3 with the LAME encoder inside your browser. Everything happens inside this page: the tool reads your input, runs the calculation or conversion locally, and hands the result back to you. Nothing is transmitted, because there is no backend to transmit it to.
That design choice is deliberate. Most free tool sites upload your files to a server, process them there, and quietly keep a copy. Toolcin cannot do that — the site is a set of static files. If your connection dropped the moment the page finished loading, every tool would still work.
Decoding to MP3 with LAME
The file is decoded by ffmpeg (compiled to WebAssembly) and re-encoded with the LAME MP3 encoder at variable bitrate. That means WAV, M4A, OGG and FLAC all come out as a real MP3 that any player accepts.
The engine is about 31 MB and downloads once; the encode then runs on your CPU, so a long recording takes proportionally longer.
Quality versus size
MP3 is lossy. Re-encoding an already-compressed file loses a little each time, so convert from the best source you have and keep it. A 3-minute track typically lands between 3 and 5 MB at the default quality.
For speech, a lower bitrate is fine; for music, anything below about 128 kbps starts to sound thin on good headphones.
| Source | Result |
|---|---|
| WAV (lossless) | Best possible MP3 |
| FLAC | Effectively transparent |
| M4A / AAC | Slight second-generation loss |
| Existing MP3 | Avoid — it only degrades |
Limits
The tab must stay open and visible; a backgrounded tab gets throttled and the encode may stall. Very long files are limited by memory, not by a quota.
Good to know
- Works offline once loaded, including on flights and in locked-down networks.
- No file size limit beyond your device's own memory.
- Free to use, with no account and no usage counter.
- Results are produced locally, so they are not logged or shared with anyone.
Questions
Are my files uploaded?
No — everything runs in your browser; only the finished file is saved to your device.
Is there a size limit?
Only your device's memory. Very large videos take longer because wasm runs on one thread.
Can it convert to WAV instead?
There is a separate MP3 to WAV page that decodes losslessly.
Is my audio uploaded?
No — ffmpeg runs in the tab.
Video and audio tools
Keep going
More files tools
GIF to MP4
Turn an animated GIF into an MP4 video. The GIF is decoded and re-encoded to H.264 MP4 locally with ffmpeg.wasm.
Open toolMP4 to GIF
Turn the first seconds of a video into a looping GIF. ffmpeg.wasm scales, samples and encodes the clip to GIF inside your browser.
Open toolMute Video
Strip the sound from a video without re-encoding. The audio stream is dropped and the video is copied, so a large file finishes in seconds.
Open toolMP3 to WAV
Convert MP3 or M4A audio into uncompressed WAV. Useful when an editor or phone only accepts WAV input.
Open toolText to PDF
Turn plain text into a clean, paginated PDF. Lines wrap automatically, new pages start when needed, and nothing leaves the browser.
Open toolScreen Recorder
Record your screen or a window and save the video locally. Uses the browser screen-capture API; the file never leaves your machine and no plugin is installed.
Open tool