Change Audio Speed
Processed locally in your browser — nothing is uploaded.
Quick answer
Changing audio speed can work two ways. With pitch correction it is a time-stretch: the audio plays faster or slower while voices and music keep their natural pitch — how podcast apps do 1.25×. Without correction it is a tape effect: speeding up also raises the pitch (chipmunk), slowing down lowers it. This tool does both in your browser, nothing uploaded. First use downloads the ~10 MB engine once.
How to change audio speed
Load your audio
Drop in the file you want faster or slower. Its current duration is shown.
Set the speed and pitch mode
Choose a speed multiplier — 1.25× to speed up, 0.75× to slow down — and decide whether to keep the pitch natural (time-stretch) or let it shift (tape effect).
Apply and download
Export the re-timed audio and download it. The new duration updates as you change the speed.
Time-stretch or tape effect — which do you want?
This is the whole decision. Time-stretch (pitch correction on) changes the tempo but preserves pitch, so a sped-up voice still sounds like the same person, just talking faster. Tape effect (pitch correction off) ties pitch to speed the way an analogue tape machine does: play a reel faster and everyone sounds like a chipmunk; slower and they sound like they are underwater. Neither is "wrong" — they are for different jobs.
Under the hood the two modes are genuinely different algorithms, which explains their different limits. The tape effect simply resamples — it reads the samples out at a new rate, so pitch and tempo move together and there is nothing to smear. Time-stretching is harder work: it chops the audio into short overlapping grains and repositions them in time, which is how it holds pitch fixed but also why extreme ratios reveal artefacts the tape effect never produces.
| Goal | Mode | Why |
|---|---|---|
| Listen to a podcast faster | Time-stretch (keep pitch) | Voice stays natural at 1.25–2× |
| Fit narration to a video length | Time-stretch (keep pitch) | Tempo changes, tone does not |
| Chipmunk / deep-voice effect | Tape (let pitch shift) | The pitch change is the point |
| Retro tape / vinyl slow-down | Tape (let pitch shift) | Emulates analogue speed change |
How far can you push it before it sounds odd?
Time-stretching is excellent within a sensible range. Speech survives roughly 0.5× to 2× cleanly; beyond that, the algorithm’s smearing and flanging artefacts start to show, especially on music with sharp transients. Small changes (0.9×–1.3×) are essentially transparent. The tape effect has no such limit because it is not trying to hide anything — but of course the pitch shifts more the further you go.
If you need a large change and the artefacts start to intrude, two tricks help. Splitting the change into two smaller passes can sound cleaner than one aggressive stretch. And where the content forgives it — percussion, ambience, background texture — accepting a slight pitch shift with the tape mode often beats a heavily stretched result, because resampling stays crisp where time-stretching turns mushy.
What is speed change used for?
- Speeding up podcasts and lectures for faster listening while keeping voices natural.
- Slowing a passage of music down to transcribe or learn it.
- Fitting a voice-over to an exact video slot without re-recording.
- Creating deliberate chipmunk or slowed-and-reverb effects with the tape mode.
Is my audio uploaded to change its speed?
No. The time-stretch and resampling both run in ffmpeg.wasm inside your browser; the file is processed locally and handed back as a download with no network request. Prove it in DevTools → Network — changing speed uploads nothing. Confidential recordings never leave your device.
Related audio and video tools
If a sped-up file is now too quiet or loud, fix it with adjust audio volume or normalize audio. Only need part of the file? Trim it first. And when the speech is stuck in a video, extract the audio from the video, then re-time it here.
Your files never leave your device
Processed locally in your browser — nothing is uploaded. You can verify it yourself: open your browser’s developer tools, watch the Network tab, and use the tool — no upload request is ever made.
Frequently asked questions
How do I speed up a podcast without the chipmunk voice?
Turn pitch correction on. That time-stretches the audio, so 1.25× or 2× plays faster while voices keep their natural pitch.
What causes the chipmunk effect?
Changing speed without pitch correction — the tape effect. Faster playback raises the pitch and slower lowers it, exactly like an analogue tape machine.
How much can I speed up before it sounds bad?
Speech time-stretches cleanly from about 0.5× to 2×. Small changes are transparent; extreme ratios introduce audible smearing, especially on music.
Does slowing audio down keep the pitch?
With pitch correction on, yes — it slows the tempo while keeping pitch natural, ideal for transcribing. With it off, the pitch drops like a slowed tape.
What speed makes a 60-minute file exactly 45 minutes?
About 1.33×, since duration is inversely proportional to speed. The tool shows the resulting length as you adjust, so you can dial in a target.
Will changing speed reduce quality?
Modest changes are near-transparent. Large time-stretch ratios can introduce artefacts. The tape mode never smears but shifts pitch by design.
Is the file uploaded?
No. Everything runs locally in your browser via WebAssembly. Confirm there is no upload in your Network tab.