InfyTool
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Change video speed

Timelapse a slow demo or slow-mo a fast moment — audio kept in sync at natural pitch, on your own device.

One video · processed on your device, nothing is uploaded

No size limit · files are processed on your device and never uploaded · how it works

Advanced settings (optional)
Speed
Playback speed

Audio stays in sync with its natural pitch. 2× halves the length; 0.5× doubles it.

Runs in your browser. Files are never uploaded — you can go offline after the page loads.

How to use the Change Video Speed

  1. Drop one video.
  2. Pick a speed from 0.25× to 4× — audio stays in sync at natural pitch.
  3. Preview and download the MP4.

Easy to use

Drop files, pick options, download. Whole folders at once, no signup, no daily limit.

Best quality

The same engines the professionals use — SVGO, resvg, MozJPEG, libwebp, libavif — compiled to run in your browser.

Private & secure

Files are processed on your device and never uploaded. Close the tab and nothing remains anywhere.

Faster video, natural voices

The naïve way to speed video makes everyone sound like a cartoon. This tool time-stretches the audio to match the new speed while preserving its pitch — a 2× tutorial sounds like a brisk explainer, not a chipmunk — and keeps it frame-accurately in sync. Silent clips are detected automatically and processed video-only.

Use it to turn a rambling recording into a tight overview (2–4×), or to slow technique footage for analysis (0.25–0.5×). For audio-only files the Audio Speed Changer is quicker; and trimming first means processing seconds instead of the whole clip.

Frequently asked questions

What happens to the audio?

It is time-stretched to match (FFmpeg’s atempo), keeping natural pitch — a 2× tutorial sounds like a fast talker, not a chipmunk. Silent clips are detected and processed video-only.

What speeds work for what?

1.5–2× for tutorials and lectures; 3–4× turns a long screen recording into a quick overview; 0.5× and below for analysing motion or sports technique.

Trim VideoWatch the video, mark start and end where you pause it, cut Audio Speed ChangerLectures at 2×, transcription at 0 Compress VideoA video small enough to send

Your files never leave your device

Most online converters upload your file to a server. InfyTool ships the actual encoders to your browser as WebAssembly instead, so processing happens inside your tab — faster for batches, and nothing to delete afterwards.

  • No upload, ever. Turn off Wi-Fi after the page loads and every tool keeps working.
  • No limits. No file-size cap, no queue, no watermark, no account.
  • Runs on your CPU. Batches use several cores in parallel; nothing is throttled.

More free tools

Need graphics to work with?

InfyTool is built by the same team as these free libraries.

InfyPNGFree transparent PNG graphics for mockups and social posts. InfySVGFree SVG designs and illustrations, ready to optimise or convert. InfyIconFree SVG and PNG icons you can open directly in these tools.