About this tool
An audio speed changer makes a clip play faster or slower. Pick a speed from 0.25× to 4×, then choose whether to keep the original pitch (a true time-stretch) or let the pitch shift with the speed like an old tape or record.
Keep-pitch mode uses the SoundTouch time-stretching engine to change tempo while holding the musical pitch steady; resample mode changes speed and pitch together with your browser's OfflineAudioContext. Both run on your device — your audio never leaves your device and nothing is uploaded to a server.
Use it to slow a lecture or language recording down for careful listening, speed up an audiobook or podcast, or create a sped-up/pitch-shifted effect for music.
Frequently asked questions
What is the difference between the two modes?
Keep pitch (time-stretch) changes only the tempo, so voices and music stay at their normal pitch. Resample changes speed and pitch together — faster sounds higher, slower sounds lower — like adjusting a record's RPM.
Which formats work and is it lossless?
Load MP3, WAV, M4A and other browser-decodable files. WAV output is 16-bit PCM; MP3 output is a lossy re-encode. Time-stretching is always a re-synthesis of the audio, so it is never bit-identical to the source.
What if the pitch-preserving engine isn't available?
If the SoundTouch engine can't load, keep-pitch mode automatically falls back to resample (which does change pitch) and tells you it did, so you always get a usable file.
Is my audio uploaded?
No — decoding, stretching and encoding all happen in your browser, so the audio never leaves your device.