What format does the compressed file come out in?

Always MP3, at the bitrate you choose. MP3 is the one format every phone, email client, player and learning platform accepts, which is the point of making a file smaller in the first place.

How much smaller will it get?

A WAV shrinks by more than 90% at the default 96 kbps. A 320 kbps MP3 loses about 70%, a 192 kbps MP3 about 50%. The exact figure is shown on each row when it finishes.

Will I hear the difference?

For speech at 96 kbps, almost never. For music, 96 kbps is noticeably softer on headphones; choose 128 or 160 kbps if the file is a song rather than a conversation.

Why did my file not get smaller?

It was already encoded at or below the bitrate you picked. Re-encoding a 64 kbps MP3 at 96 kbps makes it bigger and slightly worse. Choose a lower bitrate or leave the file as it is.

Can I compress the audio in a video?

Not here: this tool accepts audio files only. Compress Video shrinks the whole video, and Video to MP3 pulls out just the sound.

Compress Audio — Shrink MP3, WAV & M4A Files, Free

Compress Audio Files

Shrink MP3, WAV, FLAC, M4A and OGG files by re-encoding them as MP3 at a lower bitrate. See the percentage saved on every file, with nothing uploaded.

No upload — runs in your browser

Batch convert & ZIP download

Free, no sign-up

Drop MP3, WAV, FLAC, OGG, M4A, AAC and other files here

Choose files

Free: up to 5 files per batch · Files never leave your device · Paste from the clipboard works too

Private by design

Your files are processed by your own device using WebAssembly and your browser's built-in codecs. Nothing is uploaded, logged or stored.

Fast & offline-ready

No queue, no waiting for a server. Once the page has loaded it even works without a connection.

Works everywhere

Chrome, Edge, Firefox and Safari on Windows, macOS, Linux, Android and iOS. No app to install.

What "compress" means for audio

Unlike a ZIP, which packs bytes without changing them, audio compression works by storing less of the sound. The tool decodes your file with the browser's own decoder and re-encodes it as MP3 through the LAME encoder, a 300 KB WebAssembly module fetched the first time you use it. The bitrate you pick sets how many kilobits each second may use, and the row reports the result as a percentage, for example "−85%", as soon as the file is done.

What to expect from different inputs

Input	Saving at 96 kbps	Saving at 64 kbps
WAV, CD quality (1,411 kbps)	About 93%	About 95%
FLAC album rip	About 88%	About 92%
MP3 at 320 kbps	70%	80%
M4A at 256 kbps	62%	75%
MP3 at 128 kbps	25%	50%
Voice note (Opus, 24 kbps)	None: it grows	None: it grows

Speech or music? Set the bitrate to match

The default of 96 kbps is chosen for the most common job: lectures, interviews, meeting recordings, podcasts and dictation. Voices occupy a narrow band and MP3 handles them well at 64–96 kbps. Music is different. Cymbals, reverb tails and dense mixes expose low bitrates quickly, so 128 kbps is the sensible floor for songs and 160 kbps if the listener will use good headphones. Sample rate and channels are preserved, so a stereo file stays stereo; converting to mono is not something this tool does.

Targets people are usually aiming for

Email attachments, which most providers cap around 20–25 MB. At 96 kbps that is roughly half an hour of audio.
Chat apps and forums with limits of 8–25 MB per upload.
Course platforms, transcription services and job applications that reject anything over a set size.
Phones with full storage, where a 300 MB folder of voice memos becomes 30 MB.

When compression will not help

Lossy files can only be re-encoded downward: a 128 kbps MP3 run at 128 kbps comes out roughly the same size and a little worse, since each lossy generation discards something new. If a file is already small, leave it alone. If the source is WAV or FLAC and you want to keep the quality rather than cut the size, WAV to FLAC halves the file without losing anything, and the Audio Converter offers the other formats with their own bitrate menus.

How to compress audio files — step by step

Drop MP3, WAV, FLAC, M4A, AAC, OGG or Opus files into the box, or click "Choose files".
Leave the bitrate at 96 kbps for speech, or raise it to 128 or 160 kbps for music.
Compression starts automatically. Each row shows a progress bar, then the percentage saved.
Download the smaller MP3s one at a time or as a ZIP, or share them from your phone.

Frequently asked questions

What format does the compressed file come out in?: Always MP3, at the bitrate you choose. MP3 is the one format every phone, email client, player and learning platform accepts, which is the point of making a file smaller in the first place.
How much smaller will it get?: A WAV shrinks by more than 90% at the default 96 kbps. A 320 kbps MP3 loses about 70%, a 192 kbps MP3 about 50%. The exact figure is shown on each row when it finishes.
Will I hear the difference?: For speech at 96 kbps, almost never. For music, 96 kbps is noticeably softer on headphones; choose 128 or 160 kbps if the file is a song rather than a conversation.
Why did my file not get smaller?: It was already encoded at or below the bitrate you picked. Re-encoding a 64 kbps MP3 at 96 kbps makes it bigger and slightly worse. Choose a lower bitrate or leave the file as it is.
Can I compress the audio in a video?: Not here: this tool accepts audio files only. Compress Video shrinks the whole video, and Video to MP3 pulls out just the sound.