MP3 Compressor
Choose audio files and a lower bitrate to shrink them: 64 kbps halves a typical MP3, voice recordings survive 32 kbps. Everything runs in your browser.
- Runs in your browser
- Free to use
About this tool
Attachments, voice notes and podcast exports are often far larger than they need to be. The MP3 Compressor re-encodes audio in your browser with FFmpeg's LAME encoder at the bitrate you choose, constant or variable, and shows the saving per file with a player to check that it still sounds right. Nothing is uploaded.
Related: WAV to MP3, Audio Cutter.
How to use it — quick steps
- 01
Add the audio files
Drop MP3, WAV or M4A files on the dashed area or choose them, up to 25 files of 50 MB each per run.
- 02
Pick the bitrate
64 kbps suits speech and podcasts, 80 kbps music you still want to enjoy; VBR adapts to the sound.
- 03
Press "Compress audio"
Each file is re-encoded with LAME inside FFmpeg; compare the sizes, play the results and download.
Key features of this tool
Constant or variable bitrate
Fixed 32 to 128 kbps, or LAME VBR ranges that spend bits only where the sound needs them.
Batch of 25 with a .zip
Every file shows its before and after size and the saving; download them one by one or all at once.
FFmpeg in your browser
The real FFmpeg, compiled to WebAssembly and loaded on first use (about 30 MB, then cached); files never leave your device.
Frequently asked questions
Which bitrate should I choose?
32 kbps for voice memos and audiobooks, 64 kbps for podcasts, 80-128 kbps when music matters. Compressing cannot add quality: a 128 kbps source re-encoded at 128 kbps only gets slightly worse.
What is VBR?
Variable bitrate: the encoder uses fewer bits in simple passages and more in complex ones, giving better quality than CBR at the same average size.
Why is the first use slow?
FFmpeg (about 30 MB) is downloaded the first time and cached; after that it starts in a second or two.
Are my files or data uploaded?
No. The tool is plain JavaScript that runs in your browser; the files or data you provide here are never uploaded to our servers.