Shrink an MP3 down to a target file size by re-encoding it at a lower, calculated bitrate.
Compress MP3 shrinks an existing MP3 by re-encoding it at a lower bitrate. It is for the common case where a recording is just too big — a long podcast, a lecture, a voicemail archive — and a modest quality trade-off is acceptable.
Three presets (speech, everyday, half-size) show sensible starting points, and the result is decoded again so you can hear precisely what you will get.
An MP3 is already lossy, so re-compressing it is a second generation of loss; the tool minimises that by encoding from the full-precision decoded audio with the LAME-derived encoder. At 64 kbps it switches to a 22.05 kHz sample rate for speech, which is how most podcast and voice-note encoders work. Size = bitrate ÷ 8 × duration.
Bring an episode under a host’s size cap.
Compress hour-long recordings.
Fit email and chat limits.
Save phone storage.
| Bitrates | 32–192 kbps |
|---|---|
| Typical savings | 128→64 kbps: −50% |
| Quality note | Second-generation lossy encode |
At 96+ kbps for music and 48+ kbps for speech most people will not.
No; use the Metadata Editor afterwards.
MP3 at a controlled bitrate is the most universally compatible way to hit a specific file size on any device or platform.
No — everything happens locally in your browser. Nothing is sent to a server.
This tool runs entirely in your browser using the Web Audio API. Nothing is uploaded, stored or shared — there is no server to send your file to, so it works offline once the page has loaded.
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