How to compress an audio file
- Add your file. Drop in an MP3, WAV, M4A or any other audio file.
- Pick a preset. Choose High quality, Balanced, Small or Smallest, or set the bitrate, channels and sample rate yourself. The estimate shows the new size before you start.
- Compress. Press Compress, then preview the result to check that it still sounds good.
- Download the smaller MP3. The result shows exactly how much space you saved.
What the settings do
Bitrate
Bitrate is how much data is used for each second of audio, and it has the biggest effect on file size. Halving the bitrate roughly halves the file. 128 kbps sounds close to CD quality for most music, 64 kbps is fine for speech, and 32 kbps is intelligible for voice but noticeably muffled.
Channels
Switching from stereo to mono combines the left and right channels into one. For speech, such as lectures, podcasts, voice notes and interviews, you won't hear any difference, and the encoder can put all of its bitrate into a single channel for better quality at the same size.
Sample rate
Lower sample rates remove high frequencies. 44.1 kHz keeps the full range of hearing, 22 kHz keeps frequencies up to about 11 kHz (fine for voice), and 16 kHz matches phone-call quality. Lowering the sample rate lets low bitrates sound cleaner.
Which preset should you use?
| Preset | Settings | Good for |
|---|---|---|
| High quality | 128 kbps, original channels | Music you still want to enjoy |
| Balanced | 96 kbps, original channels | Music demos, mixed content |
| Small | 64 kbps, mono | Podcasts, lectures, interviews |
| Smallest | 32 kbps, mono, 22 kHz | Voice notes, email attachments with strict limits |
Common size limits: Gmail and Outlook attachments allow 20–25 MB, and WhatsApp allows up to 100 MB for audio files sent as documents. A one-hour lecture at the Small preset is about 29 MB. At Smallest, it's about 14 MB.
Frequently asked questions
How do I reduce the size of an MP3 file?
Open the MP3, choose a lower bitrate (for example 96 or 64 kbps), and switch to mono if it's speech. Then press Compress and download the smaller file.
Will compressing reduce the quality?
Yes, a little. Smaller files always keep less detail. Use the preview to find the lowest setting that still sounds good for your purpose.
Is this the same as dynamic range compression?
No. This tool reduces file size. To make quiet audio louder and more even, use the Volume Booster.
Are my files uploaded?
No. Compression runs entirely in your browser.