Convert
Shrink audio files without uploading them
Compress audio files down to a smaller MP3 at a target bitrate, processed entirely on your device.
For the best results: 64 kbps mono is genuinely fine for voice recordings and cuts files by 75% or more versus typical music bitrates. For anything with music, stay at 96–128 kbps, cymbals and hi-hats fall apart first below that.
Advanced settingsoptional, defaults work well
Converted entirely in your browser, your files are never uploaded. Very large files depend on your device's memory.
What is Audio Compressor?
Audio Compressor is a free file converter that shrinks audio files to a target bitrate of 64, 96 or 128 kbps so they fit in email attachments and messaging apps, compressed on your device. The audio is converted by an ffmpeg engine that runs inside your browser, so your recordings never leave your device. No upload, no queue, and no account, and once the engine has loaded it works even offline.
- ✦Runs entirely in your browser. Nothing you enter is ever uploaded
- ✦No account, no sign-up, and no data leaves your device
- ✦Works offline once the page has loaded
See it in action
A 10-second raw WAV clip weighs nearly 1 MB and there are two hundred of them to send.
What you drop in
take.wav (938 KB), target quality 96 kbps
What you get
take.mp3 at 118 KB, an eight-fold saving, with the full 10.0-second duration preserved exactly in testing.
Tip: Voice recordings tolerate 96 kbps happily; music deserves 128 or more. The compressor never trims or fades anything, duration in equals duration out.
Use cases
What people use it for
Squeeze a two-hour lecture recording under a learning platform's stubborn upload ceiling.
Shrink a podcast interview enough to send through email or a messaging app in one piece.
Slim down years of archived meeting recordings before they swallow a backup drive.
Who uses Audio Compressor?
Online course creators
compress hours of lesson audio to bitrates that stream smoothly for students on slow regional connections
Executive assistants
shrink meeting recordings so they attach to follow-up emails instead of bouncing off mailbox limits
Family archivists
condense decades of digitized voice recordings into a compact set that fits on cloud storage budgets
How it works
- 1Choose your files. They open in your browser, not on a server.
- 2Your device converts, compresses, or resizes them locally, with no upload.
- 3The converted files download straight back; nothing is kept anywhere.
Tips for the best results
- Estimate the outcome first: bitrate times duration tells you the final size before you start.
- Compress from the best copy you have, never from a file that has already been shrunk once.
- Test one representative recording at each setting before committing a whole archive to it.
- Music-heavy audio deserves the 128 kbps setting even when speech would tolerate less.
- Keep original recordings of legal or sentimental importance and archive the compressed copies alongside them.
FAQ
Frequently asked questions
How does bitrate translate into file size?
Directly and predictably: an MP3's size is essentially its bitrate multiplied by its duration. Halving the bitrate halves the file, which is the entire mechanism this compressor uses. A 128 kbps encode runs to roughly one megabyte per minute, so the 64 kbps setting lands near half a megabyte per minute, making the math easy before you commit.
Which setting should I use: 64, 96, or 128 kbps?
For pure speech, 64 kbps is remarkably serviceable, because voices concentrate their energy in a narrow band the encoder protects first. Podcasts mixing voice with theme music sit better at 96 kbps. Keep 128 kbps for anything where music genuinely matters, as it is the historical floor for acceptable musical quality in MP3.
What will compression audibly do to my recording?
Speech tends to survive with little more than a slight softening, while music shows strain first: cymbals smear, stereo width narrows, and busy passages develop a watery swirl. The encoder triages by perceptual importance, sacrificing subtle background texture before foreground voices. Preview a compressed minute of your specific material before running an irreplaceable archive through.
Does compressing happen privately?
Fully. The re-encode is performed by ffmpeg running as WebAssembly in your own tab, meaning your board meetings, counseling sessions, or draft episodes are never transmitted anywhere in any form. Once the engine has been cached by an earlier visit, the compressor even works with the connection down, which no upload-based service can claim.
Can I compress an MP3 that is already low bitrate?
You can, but expect diminishing returns and compounding damage. Re-encoding forces the encoder to re-approximate audio that is already an approximation, stacking a second generation of artefacts on the first. Dropping 320 kbps music to 96 works well; dropping 96 to 64 saves a third of the space at a real cost in clarity.
How do I make an audio file smaller for email?
Run it through this compressor at 64 or 96 kbps, which typically cuts a voice recording to a fraction of its original size, then attach the downloaded MP3. Because the shrinking happens in your browser, a sensitive work call is never exposed to a third-party site on the way to being emailed.
Is this an AI audio compressor?
No. It re-encodes your file with ffmpeg's standard MP3 encoder at the bitrate you select, a deterministic process with no model, no cloud, and no surprises: identical settings always give an identical file. That predictability is a feature, since compression for upload limits needs exact, repeatable results, not creative interpretation.
What is the smallest usable bitrate for speech?
Of the options here, 64 kbps is the sensible floor for stereo speech, keeping voices clearly intelligible for lectures, interviews, and dictation. Going lower than that in MP3 tends to make sibilants swim and listening fatiguing over long sessions, so the tool deliberately stops where everyday usefulness ends.
Are there any usage limits?
None. Everything is generated locally in your browser, so there is no server cost, no metering, and no daily cap, use it as many times as you like, completely free.
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