Audio Speed Changer — Pitch-Preserving 0.25–4×, In-Browser

How to use

1. Drop an audio file.
2. Pick a preset or set a custom speed (0.25–4).
3. Press Process — the engine loads once (~30 MB) on first use.
4. Download the pitch-preserved result.

About this tool

Speed up a lecture by 2× or slow a riff to 0.75× without anyone sounding like a chipmunk: this tool drives FFmpeg's atempo filter, which stretches time while preserving pitch, entirely inside your browser. Pick a preset — 0.75, 1.25, 1.5, 1.75 or 2× — or dial any custom rate from 0.25 to 4 with the slider and number box; values beyond a single filter's clean range are automatically chained (4× runs as two 2× stages, 0.25× as two 0.5× stages) so extreme speeds stay smooth. The first run loads a one-time ~30 MB WebAssembly conversion engine, after which processing is local and quick. Output keeps your original format and downloads straight from the page. Your file never leaves this page — processing runs entirely in your browser; nothing is uploaded and the data is dropped from memory when you close the tab.

FAQ

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