Free tool

Compress MP3 a smaller file, the same recording.

Drop MP3 files, pick a bitrate, download smaller MP3s. The new size shows next to the old one. Several at once.

MP3 compressor at a glance

content.win compresses a folder of long recordings in one drop, with no queue and no daily cap.

Works with
MP3, and WAV, M4A, AAC, OGG or FLAC when the result should be a small MP3.
Comes back as
MP3 at the bitrate you choose, with the new size next to the old one.
Runs
In your browser.
Limits
No daily limit and no cap on how many files.
Price
Free. No account, no watermark.

How to compress an MP3

  1. Drop the MP3 files in. Several at once is fine.
  2. Pick a bitrate. 128 kbps halves a 256 kbps file and keeps speech and most music clear; 96 kbps for the smallest file; mono halves it again for anything spoken.
  3. Download. Each card shows the new size next to the old one. One button downloads the lot.

How small it gets

320 to 128 kbps
Two and a half times smaller: a 10 MB track becomes 4 MB.
Stereo to mono
Half the size again, with nothing lost on a spoken recording.
Under 10 MB
A one-hour talk at 96 kbps mono is about 43 MB; a ten-minute one at 128 kbps mono is about 9 MB. Email limits are usually 25 MB, WhatsApp 100 MB.
Per minute
About 0.7 MB at 96 kbps, 1 MB at 128, 1.4 MB at 192, 2.3 MB at 320. Mono halves those.

About quality

  • Compressing an MP3 re-encodes it at the new bitrate. Going from 320 or 256 to 192 kbps is inaudible to almost everyone; 128 kbps is still clear for speech and casual listening; below that music starts to sound dull.
  • Compressing cannot raise quality, and compressing an already low-bitrate file gains little. Keep the original if you may need it again.

Questions people ask

How do I compress an MP3 without losing quality?

Pick 192 kbps if the file is 256 or 320 kbps: the file shrinks by a third to a half and the difference is inaudible to almost everyone. Any lower and you trade a little quality for size.

Can I compress an MP3 to under 10 MB?

Yes. At 128 kbps mono ten minutes is about 9 MB; at 96 kbps mono, thirteen minutes. The card shows the new size, so try a lower bitrate if it is still too big.

What bitrate for a voice recording?

128 kbps mono for a podcast or interview, 96 kbps mono for a memo or a lecture you only need to hear.

Can I convert several files at once?

Yes. Drop them all; each comes back named after the original, and one button downloads the lot.

Can I compress WAV, M4A or FLAC into a small MP3?

Yes. Drop them here; they come out as MP3 at the bitrate you pick.