AnyTool
Your files never leave your device. All processing happens locally in your browser.

How do I speed up or slow down a video while keeping the audio pitch natural?

Open AnyTool's Video Speed, drop in a clip, and set a speed from 0.25x to 4x. The audio pitch is preserved — voices stay natural with no chipmunk effect — thanks to ffmpeg atempo tempo-correction, and a live playbackRate preview shows the result instantly. You can keep or remove the audio. It all runs with a self-hosted ffmpeg engine in your browser: the video is never uploaded, the engine is bundled (no CDN), and there is no watermark or size cap.

  • Change speed 0.25x–4x with a live preview
  • Audio pitch preserved (no chipmunk) via atempo tempo-correction
  • Keep-audio or remove-audio option; self-hosted engine, no CDN
  • 100% in your browser — no signup, no watermark, no cap

What is

Video speed change

Changing video speed retimes a clip to play faster or slower by a chosen multiplier. Done well, the audio is tempo-corrected so its pitch stays the same — voices sound natural rather than high-pitched (sped up) or deep (slowed down). Client-side speed change re-encodes the video and audio in the browser, so the file is never uploaded.

Video Tools

Related terms

playback speedslow motionpitch correctionatempoffmpeg

How to Change Video Speed

Speed up or slow down a video in your browser.

30 secWeb browser
  1. 1

    Add a video

    Drop in a clip — it stays on your device.

  2. 2

    Set the speed

    Choose a speed from 0.25x to 4x and keep or remove audio; check the live preview.

  3. 3

    Export

    Render and download — pitch stays natural; nothing is uploaded.

Result: A retimed video file

Frequently Asked Questions

No — the audio pitch is preserved, so voices stay natural at any speed.

It uses ffmpeg atempo tempo-correction, unlike many rivals (such as VidShift or Clideo) that do not preserve pitch.

Anywhere from 0.25x (slow motion) to 4x (fast), with a live preview.

The in-browser preview uses playbackRate so you see the result instantly before exporting.

No upload — it runs entirely in your browser, and you can keep or remove the audio track.

The file never leaves your device and there is no size cap, signup or watermark.

Detailed Explanation

Methodology

How the Video Speed Changer Works

AnyTool changes video speed entirely in the browser using a self-hosted single-threaded ffmpeg.wasm engine — the core (ffmpeg-core.js + the 32 MB wasm) is bundled from npm and served as a same-origin asset, so nothing is fetched from a CDN. A live HTML5 playbackRate preview shows the new speed instantly. On apply, the clip is written to ffmpeg's virtual filesystem (MEMFS) and the video presentation timestamps are rescaled with setpts=(1/speed)*PTS; the audio is retimed with the atempo filter to preserve pitch so voices sound natural. Because atempo only accepts 0.5–2.0 per pass, factors outside that range are chained (for example 4× = atempo=2.0,atempo=2.0); you can also drop audio entirely with -an. The result is read back as an MP4 blob. Single-threaded is deliberate: the multi-threaded core needs SharedArrayBuffer + cross-origin isolation (COOP/COEP), which would block cross-origin ad iframes.

  • Runs client-side — the video is never uploaded
  • Self-hosted ffmpeg core (bundled) — no CDN
  • setpts=(1/speed)*PTS retimes the video
  • Chained atempo (0.5–2.0 per pass) preserves audio pitch
  • Optional -an to drop audio; live playbackRate preview
  • No backend, no watermark, no size cap
Privacy & Security

Pitch-preserved Audio & Privacy

Many online speed changers upload your file and simply resample the audio, shifting the pitch so voices sound chipmunked or slowed. AnyTool retimes audio with chained atempo to keep the original pitch, all locally, so the clip never leaves your browser, there is no size cap or watermark, and it works offline after the first load.

Video speed change: AnyTool vs typical tools
CapabilityAnyToolTypical tools
Data handlingIn your browserOften uploaded
Audio pitchPreservedOften shifted
Speed rangeAny (chained atempo)Limited
Live previewplaybackRateVaries
CostFree, no signupFree/limited

AnyTool is a privacy-first client-side speed changer — retiming runs locally and nothing is uploaded.