Change Speed
Change Speed makes a track play faster or slower without altering its pitch, thanks to ffmpeg's atempo filter. Speed up a lecture, slow down a track to learn it, or nudge timing to fit a video — all done privately in your browser.
Add your audio file
The file is read by your browser and stays on your device — there is no upload step.
Your audio
The work runs in this tab. Nothing is sent anywhere, and the download is generated locally.
Output —Load audio
How to use Change Speed
- 01Upload
Add your audio
Drop your file in and play it to hear the original speed.
- 02Customize
Set the speed
Use the slider or a preset from 0.5× to 2× to speed up or slow down.
- 03Process
Export
Export to render the audio at its new speed.
What changing speed does
Makes the recording play faster or slower. Common for fitting a voiceover to a fixed length, or for slowing a passage down to transcribe it.
What does not change
The content and the channels. Pitch is the thing to watch: changing speed the simple way moves pitch with it, which is the chipmunk effect. Tempo-preserving speed change keeps the pitch and costs a little smearing on sharp transients instead.
Supported formats
- MP3
- WAV
- M4A
- OGG
- FLAC
- Maximum file size —
- bounded by your device's memory
- Processed by —
- FFmpeg (WebAssembly), on your device
Your file, and what the page does
Your file is never uploaded. Change Speed reads it into this browser tab and processes it with FFmpeg compiled to WebAssembly on your own device. There is no upload endpoint in the application and no copy on any server — closing the tab discards it.
That is also why processing takes longer here than on a site that uploads: your device is doing the work rather than a rack of servers. The trade is that the file never leaves it.
What the page does send or fetch
- The processing engine, once
- The first time you use any video or audio tool, the browser downloads the FFmpeg WebAssembly build (~30MB) from the jsDelivr CDN and reuses the cached copy afterwards. That is a file coming to you — no part of your own file is in the request.
- Ads on the page
- The site is funded by advertising, so the page loads Google AdSense. That carries the usual web basics — IP address, browser, referring page — as on any ad-supported site.
- An anonymous usage counter
- When Change Speed finishes we record that the tool ran, whether it succeeded and how long it took. No file data, no identifier, no cookie.
Your file is not on that list. How this works.
Frequently asked questions
No — pitch is preserved, so faster audio doesn't sound high-pitched or 'chipmunky'.
From half speed to several times faster; extreme changes are chained internally to stay clean.
Yes — slowing speech down without pitch change makes it much easier to follow.
Yes — Change Speed is completely free. There's no account, sign-up, watermark or limit.
No. It runs in any modern browser — Chrome, Edge, Safari, Firefox, Brave — with nothing to download or install.
Looking for something else?
- You want pitch changed but not speedPitch Shift
- It is simply too longTrim Audio
- The gaps are the problemRemove Silence
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