No upload, 100% local, no account

Audio speed

Speed up a podcast or slow down a song without the chipmunk effect, pitch is preserved. Everything runs in your browser; your file never leaves your device.

How Audio speed works

Audio speed lets you speed up or slow down a track from 0.25× to 4× while keeping the original pitch, so voices stay natural instead of turning into chipmunks or growls. Speed up a podcast or lecture to save time, or slow a song down to transcribe a solo or learn a language phrase by phrase.

It uses ffmpeg's atempo filter compiled to WebAssembly, which stretches the timeline without shifting frequencies, so the pitch stays correct across the full 0.25× to 4× range. No account, no watermark.

Frequently asked questions

Are my files uploaded to a server?

No. ffmpeg compiled to WebAssembly changes the playback speed in this browser tab, your file is read into memory on your own device and processed there with the atempo filter (chained when needed so the pitch stays natural), and the result is offered as a local download. Nothing reaches Sunasty or any third party. Open your browser's DevTools, go to the Network tab and watch: no request carries your audio.

Does changing the speed change the pitch?

No. This tool preserves pitch using time-stretching (ffmpeg atempo), so a sped-up voice still sounds natural rather than high-pitched. To change both speed and pitch together (a tape effect) you would need a different tool.

What speed range is supported?

From 0.25× (four times slower) to 4× (four times faster). Because the underlying filter only accepts 0.5×–2× per stage, the tool automatically chains stages to reach the speed you ask for.

Does it keep my original format?

Yes. The output uses the same format as your input (MP3 stays MP3, WAV stays WAV, and so on).

Does it work offline?

Yes, once the page has loaded. Because the processing happens on your device, you can disconnect from the network and the tool keeps working. This is the clearest proof that your data never leaves your machine.

Is it free? Do I need an account?

It is completely free and requires no sign-up. There are no watermarks, no daily limits and no tracking cookies needed to use the tool.