Audio Compressor
Shrink MP3 / WAV / M4A by bitrate tier or to a target size
Drag & drop files here
or browse files
Shrink MP3 / WAV / M4A / OGG / FLAC audio to a smaller size
About this tool
Lecture recordings, meeting notes and audiobooks routinely run to hundreds of MB - too big for chat apps and wasteful on cloud storage. What you need is compression, not conversion. This tool offers two modes: compress by bitrate tier (five steps from 320k down to 48k) or compress to a target size (type "20 MB" and the required bitrate is derived from the duration).
Spoken-word content is informationally sparse: 64k mono MP3 sounds clean and typically lands at a tenth of the original size. Music wants 128k or more before audible dulling sets in. Output as MP3 (best compatibility), M4A (better quality per bit) or OGG (efficient open codec).
Compression runs on FFmpeg compiled to WebAssembly inside your browser: the audio never leaves your device, and the finished file downloads straight from your machine.
Features
- Five bitrate tiers (320k / 192k / 128k / 96k / 48k) with one click
- Target-size mode: enter the MB, the bitrate is derived from duration
- MP3 / M4A / OGG output formats
- Before/after size comparison with live progress and cancel
- Fully local processing - private recordings never leave the device
How to use
- Drop the audio file - duration and current bitrate are read
- Choose compress-by-bitrate or compress-to-target-size
- Click Compress and watch the progress bar
- Compare sizes, audition the result and download
Frequently asked questions
- How small is too small?
- Pure speech survives 64k or even 48k mono cleanly - an hour lands around 30 MB. Radio-style content with background music wants 96k-128k. Music below 128k starts to sound dull. When in doubt, try 96k first and move up if it bothers you.
- How does target-size mode work?
- The tool reads the duration and derives the total bitrate from target size divided by time (reserving container overhead), then encodes once at that bitrate. Results land within roughly ±10% of the target; if your target exceeds the original size the page tells you compression is unnecessary.
- Why does WAV shrink the most?
- WAV is uncompressed PCM - one stereo minute is about 10 MB - so any lossy codec is a 10x-plus reduction by definition. If your recorder outputs WAV, converting to MP3/M4A is itself the biggest win.
- Will quality suffer, and is anything uploaded?
- Lossy compression always discards something, but speech and everyday music are hard to tell apart at 96k and above; your source file stays untouched so you can experiment freely. And no: this site has no backend able to receive audio - everything happens in your browser memory.