Audio Compressor
Free audio compressor. Shrink MP3 and WAV file size, or convert between them, all in your browser with no watermark.
Audio Compressor is a free online audio compressor. Drop an MP3, WAV, OGG, FLAC, M4A, or AAC file and it re-encodes it smaller. For MP3 you pick a bitrate from 320 down to 64 kbps. For both formats you can drop the sample rate and fold stereo down to mono, which roughly halves the size again. It also doubles as a converter: MP3 to WAV, WAV to MP3, or anything your browser decodes into either.
Most free audio compressors on the open web upload your file to a server, run it past an ad page, and hand it back with a size cap or a watermark in the tags. None of that is needed. The Web Audio API decodes audio in the browser, and an MP3 and WAV encoder run right next to it. Audio Compressor re-encodes locally and gives you a clean file.
- 01Drop an audio file (mp3, wav, ogg, flac, m4a, aac), or click to pick one.
- 02Pick the output format: MP3 for a small file, WAV for lossless.
- 03For MP3, pick a bitrate. Lower is smaller. 128 kbps is a good default, 64 kbps for voice.
- 04Optionally drop the sample rate or switch to mono for extra shrink.
- 05Click Compress. The estimate updates as you change settings; the final size shows when it finishes.
- 06Download. The file saves as <source>.mp3 or <source>.wav.
- MP3 encoding is single-threaded in your browser. A 5-minute track encodes in a few seconds on most machines; the progress bar is honest.
- MP3 is lossy. Re-compressing an already-low MP3 to an even lower bitrate loses more quality. Compress from the highest-quality source you have.
- WAV is lossless and large. To shrink a WAV meaningfully, drop the sample rate and switch to mono, or just export it as MP3.
- Estimated size for MP3 is bitrate times duration, which is accurate within a few percent. WAV estimates are exact.
- Very long files (multi-hour) can strain browser memory, since decoding holds the full uncompressed audio in RAM. Split long files first if your machine struggles.
- Nothing leaves your machine. No upload, no server, no account.
Is Audio Compressor free, and does it watermark the output?
Yes, it’s free. No account, no upload, no watermark. The MP3 or WAV you download is clean.
How do I make an MP3 smaller?
Drop the MP3, keep the format on MP3, and pick a lower bitrate. Going from 320 to 128 kbps cuts the size to roughly a third. Switching to mono halves it again.
Can I convert WAV to MP3, or MP3 to WAV?
Yes. Drop the file and pick the other format. WAV to MP3 shrinks the file a lot. MP3 to WAV makes it larger and lossless, useful when an editor needs uncompressed input.
What bitrate should I pick?
128 kbps is a solid default for music on the web. 192 to 256 kbps for higher quality, 64 to 96 kbps for spoken voice where small size matters more than fidelity, and 320 kbps when you want the most quality MP3 can give.
Does lowering the sample rate or going mono actually help?
For WAV, both directly cut the size, since WAV size is sample rate times channels times duration. For MP3, the bitrate is the main lever, but mono lets the encoder spend all the bits on one channel, so a mono MP3 at the same bitrate sounds better.
What input formats can I compress?
Anything your browser can decode: mp3, wav, ogg, flac, m4a, aac, opus. Chrome and Edge decode the broadest set.
Does it upload my file to a server?
No. Everything runs in your browser. The Web Audio API decodes the audio locally, then it’s re-encoded and handed to you as a download link.
Why is my WAV bigger than the original after compressing?
WAV is uncompressed. If your source was an MP3, converting it to WAV will always be larger. Pick MP3 as the output format if your goal is a smaller file.
Your AI forgets. Astryke doesn’t.
These tools stay free. Astryke Hub is the one you pay for: a board your coding agent reads at the start of a session and writes back to at the end, so it never opens cold again.
Start free14 days free, no card. Founding price $12 a month after that.