Compress audio files
Shrink music, voice memos and recordings with bitrate, mono and sample-rate controls.
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Choose filesMP3 · WAV · AAC · FLAC · M4A · AIFF · WMA
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How to compress audio files
Add your files
Drop files on the box, paste them or choose them from your device. Nothing is uploaded.
Check the settings
The default preset suits most files. Change quality, size or format if you need a smaller file.
Download the result
Save each file or all of them as one ZIP. If a file cannot get smaller, you keep the original.
Audio formats we compress
Where audio file size comes from
Audio is either uncompressed PCM, lossless, or lossy, and the three differ by an order of magnitude in size. Uncompressed PCM, as found in WAV and AIFF files, is fixed by the sample rate, bit depth and channels: CD quality (44.1 kHz, 16-bit, stereo) is 1,411 kbps, about 10.6 MB per minute. Lossless codecs such as FLAC and ALAC store exactly the same samples in less space. Lossy codecs such as MP3, AAC and Opus remove what the ear is unlikely to notice and are sized purely by their bitrate:
| Bitrate | Per minute | Per hour | Good for |
|---|---|---|---|
| 32 kbps mono | 0.24 MB | 14 MB | Dictation, voicemail |
| 64 kbps mono | 0.48 MB | 29 MB | Lectures, interviews, podcasts with speech only |
| 128 kbps stereo | 0.96 MB | 58 MB | Everyday music listening |
| 256 kbps stereo | 1.92 MB | 115 MB | Music with a margin for good headphones |
What the settings do
- Format. AAC (in an M4A file) and Opus give the best quality per bit; MP3 plays on the widest range of old devices; FLAC is lossless. Automatic keeps the format, except that WAV and AIFF become MP3; if your browser cannot create AAC, the result is Opus.
- Bitrate. The main size control for lossy formats. Halving the bitrate halves the file.
- Mono or stereo. Speech recorded with one microphone gains nothing from stereo. Mono lets the encoder put all its bits into one channel.
- Sample rate. 44.1 or 48 kHz for music; 22.05–24 kHz is enough for speech in MP3 and saves bits for what matters.
Starting from a lossless or uncompressed file gives the best result, because there is only one generation of loss. Re-compressing an MP3 or AAC to a lower bitrate works, but quality drops faster than with a fresh encode, so do not go lower than you need. If the new file would not be smaller than the original, the tool keeps your original.
Recommendations by situation
- Recorded lecture or meeting. Mono, 48–64 kbps, 24 kHz, with MP3 as the output (AAC in Chrome and Edge on Windows starts at 96 kbps). A two-hour recording fits into about 43–58 MB and stays perfectly intelligible.
- Song or demo for friends. AAC or MP3 at 160–192 kbps, stereo. Small enough for any messenger, good enough for headphones.
- Voice message that will not send. Mono, 32–48 kbps as MP3 or Opus, which keeps a five-minute message under 2 MB.
- Audio for a website or app. Opus or AAC at 96–128 kbps, with silence trimmed at the start and end.
- Archive of recordings. FLAC, so nothing is lost and the files are still considerably smaller than WAV.
Audio formats in the browser
Decoding and encoding run on your device. The tool reads MP3, AAC and M4A, WAV, FLAC, Ogg Vorbis and Opus through the browser's WebCodecs interface; AIFF is uncompressed PCM that the tool reads with its own code. AAC and Opus are written by the browser's own encoders, while MP3 is written by the open-source LAME encoder and FLAC by libFLAC, both shipped with the tool, so WAV and AIFF can become MP3, FLAC or WAV even in browsers without WebCodecs. Firefox has no AAC encoder, so it produces Opus instead. WMA is the exception: browsers have no decoder for Windows Media formats, so the WMA page explains how to convert those files first. Audio jobs are far lighter than video: in our tests on a fast PC, a minute of WAV became an MP3 in about 2 seconds.
Audio compression questions
Which audio format gives the smallest file?
Opus is the most efficient at low bitrates, closely followed by AAC. For speech, Opus at 32 kbps, the lowest setting here, still sounds clear, but very old players do not support it; AAC is the safer choice for sharing.
Can I compress audio without losing quality?
Yes, by converting uncompressed WAV or AIFF to FLAC. Lossy files such as MP3 cannot be made much smaller without a further loss.
Does it work with recordings from my phone?
Yes. iPhone Voice Memos are M4A files, and most Android recorders save M4A, AAC or MP3, all of which the tool reads (except memos recorded with the Lossless setting, which use ALAC, a codec browsers cannot decode); see the M4A page for tips on long recordings. Phone recordings of speech are usually mono already, so the bitrate is the setting that matters most.