Change audio speed
Speed up or slow down without uploading the file.
Runs in this tab. The file stays here.
This runs in your browser. Nothing is uploaded. Longer clips take longer here than they would on a fast server. That's the trade-off for not sending the file.
About Change audio speed
Speeds up or slows down audio in the browser with atempo. Pitch stays put. Nothing is uploaded.
Same atempo chain as video speed, without the picture. Useful for lectures. Ugly for music if you push it far. Pitch stays put; this isn't a tape slowdown and not a keyframed tempo map. Lectures at 1.5× are the usual job.
Change audio speed runs FFmpeg compiled to WebAssembly in this tab. The first visit of a video or audio tool fetches about 30 MB from this origin; after that it can stay cached. Your file isn't in that download and isn't POSTed anywhere. GPL FFmpeg, single-thread, same origin, no COEP experiment. That's the same encoder as convert, trim, and compress. This page is just a different argument list, with the same honesty about what the core can't mux.
You can open the network panel and watch. Encoding a long clip on a phone is slow because it's your CPU. That wait is the trade for not handing the file to a converter you found in a search ad. Reverse and boomerang cap duration so a two-hour file doesn't try to live backwards in RAM. If a codec inside a familiar extension is missing from this core, you get an error rather than a silent broken file. Subtitle generation and stem splitting aren't here; I won't pretend they are. Missing is better than a watermarked demo.
How to use Change audio speed
- 1Drop audio.
- 2Set speed.
- 3Click Change speed, then download.
What it won't do
- Re-encodes to MP3.
- No independent pitch control.
- Speed is uniform across the file.
Common questions
Does change audio speed upload the file?
No. atempo runs in the same local FFmpeg build as the other audio tools. First visit still pays the encoder download; the recording itself never leaves the device.
Does pitch change?
No. atempo keeps pitch. It isn't a tape slowdown and not a vinyl effect. Extreme values still sound like a denser talker, not a chipmunk, which is usually what you want for a lecture at 1.5×.
Can I change pitch without speed?
Not on this page. That's a different filter and a different product. Speed is uniform across the whole file; keyframed tempo maps belong in a DAW.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation