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First run downloads FFmpeg (~25 MB) once in this browser. Compression runs locally — no server upload.

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Compress an MP3 file

Shrink an MP3 by re-encoding it at a lower bitrate. Compare the new size, then download the smaller file — free, no sign-in.

What is an MP3 compressor?

An MP3 compressor makes an MP3 file smaller by encoding it again at a lower bitrate. People search compress mp3, mp3 file compressor, or compress sound when an attachment or upload is too large. This page does that in the browser.

How the file gets smaller

One MP3 in, a smaller MP3 out.

  1. Lower bitrate: Choose 64, 96, 128, or 192 kbps. A lower number is a smaller file.

  2. Size comparison: The tool shows the original size, the new size, and the percent saved.

  3. Same format: The download is still an MP3. The filename ends in -compressed.

  4. Local compression: FFmpeg runs in this browser. The file is not uploaded.

How to compress an MP3

Three steps from a large file to a smaller one.

  1. Upload the MP3

    Drop the file you want to shrink.

  2. Pick a bitrate

    Start at 128 kbps. Move to 96 or 64 if you need a smaller file.

  3. Compress and download

    Check the saved percent, then download the MP3.

Tips

Bitrate is the size control.
  • 01

    Already-small files

    An MP3 that is already 64 kbps will not shrink at 128. Pick a bitrate below the one it uses now.

  • 02

    Voice versus music

    Speech often stays clear at 64 or 96 kbps. Music usually wants 128 or 192.

  • 03

    Each pass discards detail

    Compress once from the original. Running the new file through again removes more of the sound.

When this helps

Jobs that need a smaller MP3, not a new recording.

  1. Email and chat limits: Shrink a track so it fits an attachment limit.

  2. Upload forms: Bring a large MP3 under a size cap before you send it.

  3. A lighter copy: Keep the original and download a smaller file for sharing.

Technical details

What the compressor changes.
Encoder
LAME writes a constant-bitrate MP3 at 64, 96, 128, or 192 kbps.
What stays
The sound is re-encoded. Artwork and other tags are not copied into the new file.
Limit
MP3 files up to 200 MB.

Sources & References

Why a lower bitrate makes a smaller audio file.
  • “Even modest quality, high-fidelity stereo sound can use a substantial amount of disk space.”
    — MDN Web Docs — Audio codecs

    Audio codecs: Re-encoding at a lower bitrate is how this tool spends less space on the same track. developer.mozilla.org/en-US/docs/Web/Media/Guides/Formats/Audio_codecs

  • “Lossy compression, or irreversible compression, is a data-compression method that uses inexact approximations and partial-data discarding to represent content.”
    — MDN Web Docs — Lossy compression

    Lossy compression: MP3 already discards detail. Encoding it again at a lower bitrate discards more, and the file gets smaller. developer.mozilla.org/en-US/docs/Glossary/Lossy_compression

Frequently Asked Questions

Quick answers about this tool—open a question to read more.