Audio Speed Changer
Change audio playback speed (0.25× to 4.0×) with optional pitch preservation. Drag-and-drop or pick a file, decode with Web Audio API, choose a speed preset (7 from 0.5× to 2.0×) or enter a custom factor, toggle pitch preservation (uses OfflineAudioContext resampling to keep pitch when speed changes), and re-encode as a 16-bit PCM WAV. Pure-JS linear-interpolation resampler, pitch-shift (semitone) calculator, duration & file-size estimator, click-preventing fade in/out, audio preview before/after, history (localStorage), shareable URL, summary stats. 100% client-side.
About Audio Speed Changer
Change audio playback speed (0.25× to 4.0×) with optional pitch preservation. Drag-and-drop or pick a file, decode with Web Audio API, choose a speed preset (7 from 0.5× to 2.0×) or enter a custom factor, toggle pitch preservation (uses OfflineAudioContext resampling to keep pitch when speed changes), and re-encode as a 16-bit PCM WAV. Pure-JS linear-interpolation resampler, pitch-shift (semitone) calculator, duration & file-size estimator, click-preventing fade in/out, audio preview before/after, history (localStorage), shareable URL, summary stats. 100% client-side. Everything runs locally in your browser — your data never leaves your device.
How to use
- Enter your input in the tool above.
- Adjust any options to your preference.
- Use the Copy or Download buttons to save the result.
- Everything happens locally — your data never leaves your browser.
FAQ
How does the audio speed changer work?
Drop or pick an audio file. We decode it with the Web Audio API into raw PCM samples. With pitch preservation OFF, a pure-JS linear-interpolation resampler changes the sample rate (so both speed AND pitch shift together, like a tape). With pitch preservation ON, an OfflineAudioContext renders the buffer at the new playback rate (so the tempo changes but pitch stays the same). The result is re-encoded as a 16-bit PCM WAV.
What speed range is supported?
0.25× to 4.0×. Seven presets cover 0.5×, 0.75×, 1.0× (no change), 1.25×, 1.5×, 1.75×, and 2.0×. You can also enter any custom value in the supported range — fractional factors (e.g. 1.35×) are fine.
How is pitch shift calculated when pitch preservation is off?
Semitones = 12 × log2(speed). Doubling the speed (2.0×) raises pitch by exactly 12 semitones (one octave). Halving (0.5×) lowers it by 12 semitones. The tool shows the calculated pitch shift in the summary stats.
What extra features does this tool have compared to others?
(1) 7 speed presets (0.5× to 2.0×) + custom input. (2) Speed validation (0.25× to 4.0×). (3) Pitch preservation toggle (OfflineAudioContext resampling). (4) Pure-JS linear-interpolation resampler. (5) Pitch-shift (semitone) calculator. (6) Duration calculator (new duration = original / speed). (7) File-size estimator. (8) Pure-JS 44-byte RIFF WAV encoder (16-bit PCM). (9) Timestamped filename generator. (10) History (localStorage, last 20). (11) Shareable URL settings. (12) Drag-and-drop file input. (13) Summary stats (original duration, new duration, speed factor, pitch shift). (14) Audio preview before & after. (15) Click-preventing fade in/out at boundaries.
Is my data sent anywhere?
No. The audio file you load, decoded samples, and output WAV never leave your browser. There is no upload. Speed-change metadata in history is stored in localStorage on this device only.
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