Audio Compressor — Free, Browser-Based
Shrink audio files for email, podcasting, or storage. Re-encode MP3, AAC, OGG, or WAV at a lower bitrate or downsample. Powered by ffmpeg.wasm — your audio stays local.
How to compress an MP3 or audio file in your browser
- Drop your audio file. Drag in an MP3, AAC, OGG, WAV, M4A, or FLAC. First use loads ffmpeg.wasm (~25 MB, cached after).
- Pick a target bitrate. Choose 64 kbps (voice/podcast, smallest), 128 kbps (balanced), or 192 kbps (music, better quality).
- Optional: downmix to mono. For voice memos or podcasts, mono cuts file size in half with no perceptual loss.
- Download compressed audio. Click Compress. A 30 MB file typically shrinks to 5–10 MB depending on settings.
Use Cases
Frequently Asked Questions
Are my files uploaded?
No. Compression runs entirely in your browser via ffmpeg.wasm. Files never leave your device.
How much can it shrink an audio file?
60–80% reduction is typical going from 320 kbps stereo to 128 kbps stereo, or 80–90% going to 64 kbps mono.
Will quality drop?
Yes — lossy re-encoding always loses some fidelity. 128 kbps is transparent for speech; for music, prefer 192 kbps.
What formats are supported?
Input: MP3, AAC, M4A, OGG, WAV, FLAC, OPUS. Output: MP3, AAC, OGG.
Can I batch compress?
Yes. Drop multiple files; apply the same preset to all and download as ZIP.
Is there a length limit?
No hard limit. 2+ hour files work on most laptops; processing time scales with duration.
MP3 bitrate vs file size vs what you can actually hear
Bitrate is the single knob that decides both size and quality: it is literally how many kilobits each second of audio is allowed. Sizes below are for a 3-minute track; the perceptual notes are where most listeners stop being able to tell the difference in a blind test.
| Bitrate | 3-minute file | What you lose | Right for |
|---|---|---|---|
| 64 kbps | ~1.4 MB | Audible smearing on cymbals and applause | Voice memos, lecture recordings |
| 96 kbps | ~2.1 MB | Noticeable on music through headphones | Podcasts, spoken word |
| 128 kbps | ~2.8 MB | The classic "good enough" line for casual listening | Music on phone speakers or in a car |
| 192 kbps | ~4.2 MB | Very hard to distinguish from source on most gear | General music library |
| 256 kbps | ~5.6 MB | Transparent for nearly all listeners | Music you care about |
| 320 kbps | ~7.0 MB | Maximum for MP3 — no further gain | Archiving, mastering handoffs |
- Sample rate is a separate knob: 22,050 Hz halves the size again but caps the top frequency near 11 kHz, which is fine for speech and audibly dull for music. Leave it at 44,100 Hz unless the file is voice only.
- Compression is lossy and one-way. Re-encoding an already-compressed 128 kbps file at 320 kbps makes it larger without restoring anything — always start from the highest-quality source you have.
- Mono halves the size of a stereo file at the same bitrate and is the correct choice for a single-speaker recording.
Related tools
More free, in-browser tools from the Video & Audio set — every one runs locally, with no sign-up and no upload.