Compress MP3
Shrink an MP3 by re-encoding it at a lower bitrate — in your browser.
Select an audio file
Re-encode an MP3 at a lower bitrate to shrink it — pick the bitrate below. Runs in your browser.
Click to choose, or drop a file here
About compressing an MP3
MP3 file size is set almost entirely by its bitrate — kilobits per second of audio. A 320 kbps file is about 2.5× the size of a 128 kbps one. Re-encoding an existing MP3 at a lower bitrate is the direct way to make it smaller for email, a form upload, or a website, and that's what this tool does, in your browser.
It decodes the MP3 to raw audio and re-encodes it with a JavaScript port of the LAME encoder at the bitrate you pick. Because MP3 is lossy, this second encode discards more detail — but at 192 kbps it's hard to hear on most material, and 128 kbps is genuinely fine for speech and podcasts. The tool shows the before and after size.
There's no "target size" mode here — you choose the bitrate directly, and lower bitrate means smaller file. Nothing is uploaded; the encode runs on your device and is CPU-bound, so a long file takes a moment.
Supported files
Accepts an MP3. Produces a smaller MP3 at 128, 192, 256 or 320 kbps.
Is my file uploaded?
No. The MP3 is decoded and re-encoded entirely in your browser with an in-browser LAME port.
Common problems
- It barely got smaller
- The original was probably already a low bitrate. Check its properties — you can't shrink a 128 kbps file much without it sounding bad.
How to Compress MP3
- 1
Add your MP3
Drop in the file you want smaller.
- 2
Pick a bitrate
128 kbps for voice, 192 for a good default — lower bitrate, smaller file.
- 3
Compress and download
Click Compress; it's re-encoded in your browser.
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Compress MP3 — frequently asked questions
How much smaller will it be?+
It depends on the original bitrate. Going from 320 to 128 kbps roughly halves the file; the tool shows the before/after size.
Is quality lost?+
Yes — re-encoding an MP3 at a lower bitrate discards more detail. 192 kbps is a good balance; 128 is fine for speech.
Is my file uploaded?+
No. It's decoded and re-encoded in your browser with a JavaScript LAME port.
Can I set a target size?+
Not directly here — pick the bitrate. Lower bitrate, smaller file.
Do you upload my files to a server?+
No — every tool here processes your files entirely on your device, and nothing is uploaded to a server. The only exception is the AI tools, which send the extracted text (not the file) to Claude to do their work.
Is there a file size limit?+
There's no artificial limit we impose, but since processing happens in your browser, very large files (500+ MB or 1,000+ pages) are limited by your device's memory rather than by us.
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