At a glance
| Input | Any audio the browser can open |
|---|---|
| Output | MP3 or WAV |
| Speeds | 0.25x to 4x |
| Pitch | Keep the original pitch, or let it move with the speed |
| Where it runs | Entirely in your browser — no file is uploaded to a server |
| Price | Free, with no account and no sign-up |
| Offline | Works with no connection after the first visit |
Speed without the chipmunk effect
Playing samples faster raises every frequency, which is why naive speed-up makes voices squeak. Time stretching instead repeats or removes very short segments, leaving pitch alone.
Past about 2x a slight warble appears on speech, and beyond 3x it is obvious. For a lecture at 1.5x it is entirely transparent.
Slowing down for transcription
0.75x makes fast or accented speech much easier to catch, and 0.5x is slow enough to write along with. Both keep the pitch, so the voice remains recognisable rather than becoming a drone.
Speeding up is the same tool in the other direction: most lecture and podcast audio is comfortably intelligible at 1.5x once you are used to it, which is a third off the listening time.
Frequently asked questions
Will voices sound higher when sped up?
No — pitch is preserved by stretching time rather than resampling. Past about 2x a slight warble appears.
What speed is good for transcription?
0.75x for difficult audio, 0.5x to write along with. Both keep the voice recognisable.
Does the file get smaller when sped up?
Yes, roughly in proportion — there is less audio to store.
Something wrong with this tool, or an idea for it? Tell us