What is audio compression?
Audio compression re-encodes a sound file at a lower bitrate, removing detail that is hard to notice, so the file takes up less space. A 5-minute song saved as WAV can be 50 MB; the same song encoded as a 192 kbps MP3 is typically 7-8 MB with little audible difference on most speakers or headphones.
Everything runs directly in your browser using a local WebAssembly build of FFmpeg. Your files are never uploaded - the whole process happens on your device.
Choosing a format
MP3 is the most compatible format and plays everywhere, from phones to car stereos to old software - use it unless you have a specific reason not to.
AAC (M4A) generally sounds better than MP3 at the same bitrate. It's the default format for Apple devices and most streaming services.
OGG Vorbis is an open, royalty-free format that compares well to MP3 at the same bitrate. Good for web use or open-source projects.
WAV is uncompressed audio - no quality is lost, but the file stays large. Choose it only when you need a lossless master, not a smaller file.
Choosing a bitrate
Higher bitrates sound closer to the original but produce larger files. 96-128 kbps is enough for spoken word like podcasts and voice memos. 192 kbps is a solid balance for music. 256-320 kbps is close to transparent for most listeners and is a good choice when file size isn't the main concern.
Target file size mode
Turn on Target file size when you have a hard limit to hit, like an email attachment cap or a platform upload limit. Enter the size you want and the tool calculates the bitrate needed to land at or near that size, based on each file's duration, instead of you guessing a bitrate. The estimated output size updates live as you adjust settings. Target size mode is not available for WAV, since WAV output size is fixed by its uncompressed format.
Duration and size estimates
As soon as a file is added, its duration is read and used to estimate the compressed output size for your current settings, so you can see roughly what you'll get before you compress anything.
Comparing before and after
Once a file finishes compressing, click Preview on its row to play the original and compressed audio side by side, so you can confirm your bitrate or target-size setting didn't go too far before downloading.
How to compress an audio file
- Drop one or more audio files onto the drop zone, or click Browse files.
- Choose an output format and bitrate, or turn on target file size and enter a size.
- Check the estimated output size next to the options.
- Click Compress. Files are processed one at a time and each row shows progress while it runs.
- Preview a result, then download it from its row or grab everything as a ZIP.
Common uses
Email and messaging
Most email clients cap attachments at 25 MB. Compress a long voice memo or lecture recording to 128 kbps MP3 to fit comfortably under the limit.
Podcasts
Spoken-word content compresses well at low bitrates. 96-128 kbps MP3 keeps podcast episodes small without hurting clarity.
Music libraries
Converting a folder of WAV or FLAC masters to 256 kbps AAC or MP3 can cut storage use dramatically while staying close to transparent quality.
Web and app delivery
Smaller audio files load faster. Compress background music or sound effects to OGG or a lower MP3 bitrate before adding them to a website or app.
Frequently asked questions
Why does it download 30 MB on first use?
The audio encoder that runs in your browser is about 30 MB. It downloads once and is cached by your browser, so future visits load instantly.
Will compressing reduce audio quality?
Some quality loss is inherent to lossy formats like MP3, AAC, and OGG. A higher bitrate keeps that loss small; WAV output has no quality loss at all since it is uncompressed.
My audio format is not listed. Will it still work?
Most common formats work fine as input, including FLAC, WMA, and OPUS. Just drop the file and it will be read correctly - the output will be in your chosen format regardless of the input.
Is there a limit to how many files I can add?
No limit. Files are processed one at a time so memory from the previous file is freed before the next one starts.
How accurate is target file size mode?
The tool calculates the bitrate needed to hit your target based on each file's duration, so results usually land close to the target. Very short files can vary a bit more.