How to use the MP3 Converter converter
- Add filesClick “Choose Files” or drag them in. Each file is detected automatically, and you can mix different formats in one batch.
- Pick the output formatUse the “to” menu next to each file to choose the target format (MP3 is preselected).
- Convert and saveHit “Convert”. Everything is processed on your device, then you can download each result or a ZIP of all of them.
About MP3
MP3 MPEG-1 Audio Layer III
MP3 is the universal audio format. It shrinks music to around a tenth of CD size and plays on literally every phone, car stereo, speaker and app.
- Compression
- Lossy
- Features
- Stereo, ID3 tags
- Origin
- 1993, Fraunhofer IIS
- Best for
- Music, podcasts, audiobooks
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
What formats does the MP3 Converter support?
It accepts MP3, WAV, OGG, OGA, AAC, M4A, FLAC, OPUS, WMA, AIFF, AIF, AMR, AC3, M4R and more, and can output MP3, WAV, OGG, AAC, M4A, FLAC, OPUS, WMA, AIFF.
Is it really free?
Yes. ConvertMathly is free with no sign-up, no watermarks and no limits. The site is supported by ads.
Are my files private?
Completely. Conversion happens inside your browser — files are never uploaded to any server.
Why does the first video or audio conversion take longer?
A one-time download of the FFmpeg engine (~30 MB) is needed. It is cached afterwards, so later conversions start instantly.
Does it work on iPhone and Android?
Yes, the converter works in Safari, Chrome, Firefox and Edge on phones, tablets and computers.