How it works
- Select or drop one or more MP3, WAV or M4A files from your device.
- Choose High quality (256 kbps), Balanced (160 kbps) or Maximum compression (96 kbps).
- Select Compress audio and keep the tab open while FFmpeg processes each file locally.
- Compare the actual before and after sizes, then download the resulting MP3.
Practical example
A recording is too large to send, share or store conveniently. Add it and start with Balanced for a middle ground between file size and sound quality. After processing, compare the reported sizes and listen to the MP3. If a smaller file matters more than preserving detail, try Maximum compression; choose High quality when fidelity matters more.
Formula and explanation
Compress Audio decodes each source and re-encodes the full track as MP3 with libmp3lame at 44.1 kHz. Its three fixed presets use 256, 160 or 96 kbps.
File size is the space the audio occupies; bitrate is the amount of audio data used per second. For the same duration, a lower target bitrate generally produces a smaller MP3 but can discard more sound detail because MP3 compression is lossy.
The actual result also depends on the original codec, bitrate and content. An MP3 that is already highly compressed may shrink very little or even grow, so Cifrivo reports the measured before and after sizes instead of promising a reduction.
The tool accepts up to 10 MP3, WAV or M4A files: 100 MB each, 300 MB total and two hours each. FFmpeg WebAssembly processes them in this browser without uploading them to Cifrivo or a third party.