MP3 Compressor
Choose your channel mix and sample rate, then compress your MP3 file and preview the result before downloading — free, private, and processed entirely in your browser.
About the MP3 Compressor
Our free online MP3 compressor shrinks an MP3 file by downmixing it to mono and reducing its sample rate. That makes it easy to shrink a podcast episode, voice memo, or music track down to a size that's much easier to email, upload, or share, while still sounding great.
Unlike most online tools, compression happens entirely inside your browser using the Web Audio API — your audio file is never uploaded to a server. That means it's fast, works without an internet round-trip, and keeps your files completely private and secure.
How to Compress an MP3
Step 1
Upload your MP3 file
Drag and drop an MP3 file, or choose one from your device.
Step 2
Choose your channel mix and sample rate
Select Stereo or Mono, and pick a target sample rate to further shrink the file.
Step 3
Compress, preview, and download
Click "Compress MP3", preview the result in the built-in player, then download the compressed file.
Frequently Asked Questions
How much can I reduce an MP3 file size?
Downmixing from stereo to mono cuts the file size in half, and reducing the sample rate on top of that can shrink the file by up to 70% total, depending on the source audio.
Are my audio files uploaded to a server?
No. All audio decoding, resampling, and MP3 encoding happen 100% locally in your browser using the Web Audio API — your file is never uploaded to a server.
Will compressing reduce the audio quality?
Downmixing to mono and lowering the sample rate both reduce fidelity somewhat, which is most noticeable on music with a wide stereo image or high-frequency detail. For spoken-word content like podcasts and voice recordings, the difference is usually barely noticeable.
Can I preview the compressed audio before downloading?
Yes. Once compression finishes, a built-in audio player loads the compressed file so you can listen to it before deciding whether to download.
Does it cost money?
No. The MP3 compressor is 100% free to use, with no registration or account required.