Audio Speed Changer
An audio speed changer for lectures, podcasts, songs and voice notes: play them anywhere from half speed to double speed and keep the voice sounding natural, without the chipmunk effect. Turn off pitch preservation for the record-player effect instead. The new file has exactly the new length, and it is made in your browser with no upload.
- Runs on your device
- Web Audio
- WebCodecs · GPU
- Works offline
Updated
Drop your audio files here
How to change audio speed
Step 1: Drop your audio files on the box above.
Step 2: Drag Speed: below 1× slows down, above 1× speeds up (1.25× is the default).
Step 3: Keep Keep original pitch on for natural voices, then press Apply and download.
Good to know
Settings explained
- Keep original pitch
- Off: speed and pitch change together, like a record.
Formats
Batch-friendly: add many files and they are processed one after another — if one fails, the rest still finish.
How it runs
- Web Audio
- Audio is processed with the browser’s built-in Web Audio engine, sample-accurate and fast.
- Hardware video engine
- Video is decoded and encoded by your device’s media hardware through WebCodecs — usually several times faster than real time.
How long will it be at each speed?
The new length is simply the old length divided by the speed. The table shows a one-hour lecture, a four-minute song, and what happens to a 120 BPM song’s tempo.
| Speed | 60-minute lecture | 4:00 song | A 120 BPM song becomes |
|---|---|---|---|
| 0.5× (slowest) | 120 min | 8:00 | 60 BPM |
| 0.75× | 80 min | 5:20 | 90 BPM |
| 0.9× | 67 min | 4:27 | 108 BPM |
| 1.25× (default) | 48 min | 3:12 | 150 BPM |
| 1.5× | 40 min | 2:40 | 180 BPM |
| 2× (fastest) | 30 min | 2:00 | 240 BPM |
How do I speed up audio without changing the pitch?
Keep Keep original pitch on. The audio is then time-stretched with SoundTouch’s WSOLA method: it is cut into small overlapping pieces that are laid closer together (faster) or further apart (slower), so the duration changes while each piece keeps its original pitch. Speech stays intelligible up to about 1.5–1.75×, and slowing to 0.75× is comfortable for transcription or learning a song by ear.
Why does speeding up audio raise the pitch?
Because pitch is how fast the sound wave vibrates. Play a recording faster, as a tape or record player does, and every vibration happens sooner, so the pitch rises: 1.25× is almost four semitones higher. Switch Keep original pitch off to get that effect on purpose. For the genre versions, the nightcore maker speeds up with a higher pitch and the slowed and reverb generator slows down with a lower one.
Slow down audio for transcription or practice
- Transcribing an interview: 0.75–0.8× gives you time to type without distorting words.
- Learning a solo or a dance: 0.5–0.75× with pitch kept, so you practise in the right key.
- Language learning: 0.8× makes fast speakers easier to follow.
- Change the BPM of a song: set speed to the new BPM ÷ the old BPM (128 ÷ 120 ≈ 1.07). The slider moves in 0.05× steps, so pick the nearest value. Find the current tempo with the BPM finder.
Tips & troubleshooting
Can I change the speed of a WhatsApp voice note? Yes: save it from WhatsApp, drop the .opus file here and pick a speed. To share it widely, convert with Opus to MP3 too.
Changing a video’s speed? Use change video speed, which keeps picture and sound in sync.
Need a different key at the same speed? That is the pitch changer.
Audio Speed Changer FAQ
How do I speed up audio without changing the pitch?
Keep Keep original pitch switched on, set the speed above 1× and press Apply. Time-stretching changes the length while the pitch stays the same.
How do I slow down audio without changing the pitch?
Set the speed below 1×, down to 0.5×, with Keep original pitch on. Voices and instruments stay in their original key, just slower.
Does changing the speed reduce quality?
Moderate changes (0.75–1.5×) sound clean. Extreme ones can add a slight echo-like smear, a side effect of time-stretching. Saving as WAV or FLAC avoids an extra lossy encode.
Is my audio uploaded?
No. The speed change is calculated in your browser on your device, and the page keeps working offline once it has loaded.