Audio Compressor
Reduce audio file size by re-encoding MP3, WAV, M4A, OGG or FLAC to a smaller MP3 — pick the bitrate, go mono for voice, all in your browser.
How to Compress an Audio File in 3 Steps
Drop an Audio File
Drag any MP3, WAV, M4A, OGG or FLAC onto the left pane. Duration, channels, sample rate and size appear in the header and you can play the original.
Choose a Bitrate
128 kbps is transparent for most listeners; 64 kbps mono at 22 kHz shrinks a podcast or voice memo by 10× or more. The toolbar estimates the output size.
Compress & Download
Click Compress — encoding runs many times faster than real time. Play the result, compare sizes, then download the MP3.
Bitrate Guide
| Content | Recommended | 1 hour ≈ | Notes |
|---|---|---|---|
| Voice memo, lecture, podcast | 64 kbps mono, 22 kHz | 28 MB | Speech has little above 10 kHz; mono halves the data again |
| Audiobook, interview | 96 kbps mono | 42 MB | Slightly fuller tone, still a 10× saving on WAV |
| Music for phone / sharing | 128 kbps stereo | 56 MB | Standard streaming quality; the default here |
| Music, critical listening | 192 kbps stereo | 84 MB | Hard to tell from CD on most headphones |
| WAV / FLAC source | Any of the above | — | Uncompressed audio is ~600 MB per hour; any MP3 setting is a large win |
Audio Compressor — Frequently Asked Questions
Why is the output always MP3?
MP3 plays on every device and app ever made, and it is the only format browsers can encode purely in JavaScript without a server. AAC and Opus are slightly more efficient but need a native encoder plus a file muxer that browsers do not expose.
Will compressing an MP3 again lose quality?
A little — every lossy re-encode discards some detail. Going from 320 to 128 kbps is usually inaudible; re-encoding 128 to 128 gains nothing, so the tool keeps the original if it would not shrink.
What do Mono and 22 kHz do?
Mono mixes left and right into one channel — half the data, perfect for speech recorded on one mic. 22.05 kHz halves the sample rate, dropping frequencies above 11 kHz that speech does not use. Leave both at Keep for music.
Is my audio uploaded anywhere?
No. The file is decoded with the Web Audio API and encoded by a JavaScript MP3 encoder (lamejs) on your device. Nothing is transmitted or stored.
Why is the file size limit 200 MB?
Decoding expands audio to raw samples in memory (about 10 MB per minute of stereo). 200 MB of MP3 is around 3 hours — larger files risk running a phone browser out of memory.