How it works
- Drop your audio file. MP3, WAV, FLAC, AIFF, OGG or M4A up to 500 MB — the current BPM is detected automatically.
- Choose your target. Either a speed factor from 0.5× to 2×, or a target BPM — the detected tempo pre-fills the current BPM field.
- Listen and download. Play the stretched result, then download it in the same format as your source file.
Features
- Pitch preserved. The tempo changes, the key doesn't — no chipmunk effect when speeding up.
- Two ways to set the target. A simple speed factor, or BPM mode with automatic detection of the current tempo.
- Honest about quality. Moderate changes are very clean; the tool warns you near the extremes, where artifacts can appear.
- 100% in your browser. Your track never leaves your computer — processing runs locally with ffmpeg.wasm.
FAQ
Is this time stretch tool free?
Yes. Anonymous users get 5 free uses per day across AudioKit's free tools — no account needed. A use is only counted when you apply the stretch; loading and listening is free. AudioKit Premium removes the daily limit.
Is my audio file uploaded to a server?
No. The file is decoded, stretched and re-encoded entirely in your browser with ffmpeg.wasm and never leaves your machine. The only network call is a tiny anonymous counter that tracks your daily free quota.
Which audio formats are supported?
MP3, WAV, FLAC, AIFF, OGG and M4A files up to 500 MB. The stretched file is exported in the same format as the source: lossless stays lossless, lossy formats are re-encoded at high quality.
How far can I stretch before artifacts appear?
Honestly: moderate changes — roughly 0.8× to 1.25×, i.e. about ±20% — sound very clean. Push toward the 0.5× or 2× extremes and phasing or a metallic color can appear; that's inherent to time-stretching, not a bug. For learning a solo, slowing down to around 0.75× usually stays comfortable.
Can I convert a song to an exact BPM?
Yes — switch to BPM mode: the tool detects the current tempo (editable if it got it wrong), you type the target BPM, and the stretch factor is computed for you. Handy for locking two tracks for a mashup or fitting a beat to a project tempo. Use the BPM finder to check tempos first.