Free audio compressor, nothing uploaded.
A free audio file compressor that runs on your own device — compress audio online free, with nothing uploaded. Tell it what you need: a quality, a size in MB, or “make it 70% smaller”. It shrinks the file, then plays original and smaller version side by side so you can hear the difference before you keep it.
Add your audio file
Drag a file here, or press the button. It gets shrunk into a smaller MP3 right on your device — nothing is uploaded — and you can listen before you keep it.
MP3 · WAV · M4A · FLAC · Ogg · Opus — videos work too.
Your privacy — live proof, not a promise
- Files uploaded
- 0 bytes
- Processing
- Not started yet
- Your files
- Stay in this browser tab — gone when it closes
- Converter engine
- Not downloaded — only fetched if a format needs it
One download, and it isn’t your audio
Converting to MP3 or WAV needs no download at all. Less common formats use a built-in converter engine (32.5 MB) that comes from this site — not from some other company — downloads once, and is then saved in your browser. Your audio is never part of that download: the engine comes to your files, your files don’t go to it.
Don’t take our word for it: open your browser’s DevTools, watch the Network tab, then convert a file. You’ll see nothing carrying your audio — because this page has no upload feature at all. There is nowhere for your file to go.
Scope note, so this stays exact: the claim is about your files — they never leave this device. The site around it is not claim-free. It loads Vercel Analytics for aggregate page traffic, plus Google Analytics and Ads tags if you accept the consent prompt. Those measure page visits and store-link clicks. They never receive your audio, because nothing does. Full privacy policy.
Converted files are never stored by this page — they exist only in this tab until you download them.
Changing format, not size?
To get out of M4A, Opus, WMA or a video container, use the free online audio converter — same on-device engines, six output formats, batch queue and ZIP download.
Compress, then transcribe
Text is the ultimate compression — a one-hour recording is a few hundred kilobytes of words. The free audio to text tool transcribes on your device too.
How to compress an audio file, in three steps
No account, no software to install, and nothing to learn. The whole thing takes about as long as the file takes to play.
Add your file
Drag an audio file onto the box above, or press Choose a file. It stays on your device — there is no upload.
Say how small you want it
Pick Voice, Standard or High — or type the size you need in MB, or drag the slider to shrink by a percentage. You will see the new size before anything happens.
Listen, then download
Press Make it smaller, then tap A and B to compare the original with the shrunk version at the same moment. Happy? Download it. Not happy? Change the setting and try again — it costs nothing.
What the quality settings actually mean
Audio compression is really three dials — how much detail to keep, one ear or two, and how fine-grained the sound is. Each preset is just a sensible combination. The Voice preset is the exact recipe the BlackBox app records with: about 14.4 MB per hour, the same numbers the audio storage calculator uses. (The app encodes AAC; this page encodes MP3 — same size and character, not the same file.)
Voice
32 kbps · mono · 16 kHz
Speech-first. The same rate BlackBox records at (~14.4 MB/hour).
Standard
64 kbps · mono · 32 kHz
Clear speech with some room tone. Half the size of most voice memos.
High
128 kbps · stereo · 44.1 kHz
Music-capable. Compresses a WAV hard while staying pleasant.
How to reduce audio file size without wrecking the sound
Talking shrinks beautifully
A voice uses only a small slice of the sounds humans can hear, so recordings of people talking can be squeezed very hard and still sound clear. A one-hour meeting recording lands around 14 MB on the Voice setting. That’s why voice apps — including the BlackBox recorder — live in exactly this territory.
Music pushes back
Music uses the whole range of sound, so squeeze it too hard and you’ll hear it go dull and swirly. And squeezing an already-small file again saves almost nothing while losing a bit more quality. This page checks for both and tells you plainly when the honest answer is “leave it alone”.
Why the A/B player exists
A percentage on a slider tells you nothing about what your ears will notice. So after compressing, this page keeps both versions loaded at the same spot — tap A for the original, B for the smaller one, even mid-sentence. The most honest answer to “is this good enough?” is to listen for yourself.
Compress audio online free — your questions, answered
How much smaller can this make my audio file?+
Speech shrinks a lot: a one-hour WAV recording (~700 MB) at the Voice setting comes out around 14 MB — about 98% smaller. A typical voice memo shrinks by roughly 75%. Music is fussier: squeeze it too hard and you'll hear it. The built-in A/B player lets you listen to before-and-after so you can judge with your own ears.
Will compressing hurt the sound quality?+
A little, always — that's how compression works. The real question is whether you can hear the difference. Clear speech still sounds fine even when squeezed very hard; music does not. This page warns you when a setting will noticeably hurt speech, and the A/B player plays the original and the smaller version at the same spot so you can compare instantly.
Why would I set a target file size?+
Because that's usually the actual problem: an email won't send over 25 MB, a form only takes 10 MB, a voicemail system has a cap. Type the size you need and the page works out the best possible quality that still fits under it — and tells you honestly if the target isn't reachable for a file that long.
Is it worth compressing a file that's already small?+
Often not, and the page will tell you so. If a file is already heavily compressed, squeezing it again saves almost nothing and loses a little quality for free. When your settings land in that pointless zone, you'll see a note saying the honest answer is to leave the file alone.
Is the compressed file uploaded anywhere?+
No. Compressing happens entirely in this tab — the file is opened, shrunk and handed back to you as a download, all on your device. There is no upload feature in this page at all. The privacy panel below the tool shows the live count: files uploaded, 0 bytes.
Or record compact in the first place.
BlackBox records 24/7 at 32 kbps mono — about 14.4 MB an hour, transcribed and searchable on your phone. The files never need compressing, because they never got big. Free on iPhone and Android.