Load your clip
Choose an audio file, or a video file like an MP4 — only its audio track is used. It's saved to your on-device library for next time.
Free Online Loop Tempo Changer
Slow down or speed up an audio loop without changing pitch. Detect BPM, choose the exact bars, and export in your browser.
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Library
Tracks you load are saved here automatically — stored privately on this device only, never uploaded.
0:00 / 0:00
Vol
Choose an audio file to begin
Loop Region—
Load audio, then drag the two handles to select what loops
TempoDetected: —
BPM — tap number to type one directly
Fine adjust100%
0.5×1×1.75×
Runs fully in this tab — audio is never uploaded. Tracks you load are kept only in this browser's local storage.
How to change a loop's tempo
Pick the section that actually repeats before you touch the tempo — that's what makes the difference between a clean loop and one that stutters.
Pick the loop region
Drag the waveform handles, or tap "4 bars" / "8 bars" to snap to a clean phrase using the detected tempo.
Dial in the tempo
Type a BPM, tap the +/- steppers, or drag the Fine Adjust slider. Pitch stays exactly where it was.
Change tempo without changing pitch
Slowing audio down or speeding it up naturally also changes its pitch — like a record player running at the wrong speed. This tool uses a time-stretch algorithm (WSOLA) that decouples the two, so a loop played at 80% speed still sounds like it's in the same key.
Looping only sounds seamless when the selected region is an actual musical phrase — a clean number of bars. Dragging an arbitrary slice out of a full song will always have an audible seam no matter what processing is applied, so use the waveform handles or the bar-snap buttons to find a real loop point.
Common uses
- Slow down a praise, worship, or dance loop to learn the rhythm.
- Speed up a backing track for practice without shifting its key.
- Find and isolate the exact bars of a clip that repeat cleanly.
- Save a few go-to loops locally so they're one tap away next time.
Frequently asked questions
Does the pitch change when I speed up or slow down?
No. A time-stretch algorithm (WSOLA) keeps the pitch fixed while the tempo changes, instead of simply playing the audio faster or slower.
Is my audio uploaded anywhere?
No. Decoding and processing happen entirely in your browser via the Web Audio API. Tracks saved to the on-device library use IndexedDB, which stays private to this browser and is never sent anywhere.
What file types can I load?
Standard audio files (MP3, WAV, M4A) and video files with an audio track, such as MP4 or MOV — only the audio is decoded and used.
Why does my loop still sound slightly off?
Looping works best on a clean musical phrase. If the selected region isn't a whole number of bars, drag the waveform handles or use the "4 bars"/"8 bars" snap buttons to align it to the detected tempo.
Why doesn't the page freeze while it processes audio?
The time-stretch and BPM-detection math runs in a background Web Worker thread, separate from the thread drawing the interface, so the waveform and controls stay responsive while the CPU-heavy work happens.