BYTETOOLS

Change Video Speed

Speed up or slow down a video from 0.25× to 4× online, free. Audio stays in sync with its pitch preserved — all in your browser, nothing uploaded.

Drop a video here or click to browseYour video is processed locally and never uploaded.
Untick if your video has no sound — otherwise the conversion will fail.

What is the Change Video Speed?

The ByteTools Change Video Speed tool speeds up or slows down any clip, from quarter-speed slow motion to 4× fast-forward.

  • Speeds from 0.25× slow motion to 4× fast-forward
  • Pitch-preserving audio time-stretch keeps voices natural
  • Video and audio stay perfectly in sync
  • Optional audio-free mode for silent clips
  • 100% local processing — never uploaded
  • Standard MP4 (H.264 + AAC) output

How to use the Change Video Speed

  1. 1

    Drop a video onto the box or click to browse for one.

  2. 2

    Pick a playback speed from 0.25× to 4×.

  3. 3

    Untick “Keep audio” if the clip has no soundtrack.

  4. 4

    Click Change speed, preview the result and download the MP4.

About the Change Video Speed

The ByteTools Change Video Speed tool speeds up or slows down any clip, from quarter-speed slow motion to 4× fast-forward. The audio track is time-stretched to match, and its pitch is preserved — voices stay natural instead of turning into chipmunks when sped up or growls when slowed down.

Use it to make slow-motion replays, condense long screen recordings and tutorials, speed through lecture footage at 1.5× or 2×, or create fast-forward timelapse-style clips from real-time footage. If your video has no soundtrack at all, simply untick the audio option and only the picture is retimed.

The retiming runs 100% locally in your browser using a WebAssembly build of ffmpeg — your video is never uploaded to any server, there are no accounts and no watermarks, and the output is a standard H.264 MP4 that plays in every editor, browser and phone gallery.

Frequently asked questions

How do I speed up a video without making voices sound like chipmunks?

This tool uses a pitch-preserving time-stretch (ffmpeg's atempo filter) on the audio while retiming the video, so speech stays at its natural pitch. Even at 2× a voice sounds faster but not squeaky.

Can I slow a video down to real slow motion?

You can play it at 0.25× or 0.5×, which stretches the existing frames over more time. True buttery slow motion also needs a high original frame rate — a 60 fps source slowed to 0.5× looks smooth, while a 24 fps source will look steppier.

Does changing the speed change the file length?

Yes. A 10-minute recording at 2× becomes 5 minutes, and at 0.5× becomes 20 minutes. File size scales roughly with the new duration since the video is re-encoded at a constant quality.

Why did the conversion fail with audio enabled?

The most common cause is a video with no audio track — the audio filter then has nothing to process. Untick “Keep audio” and run it again; the video track alone will be retimed.

Is my video uploaded while changing its speed?

No. Everything is computed in your browser with WebAssembly. The clip never leaves your device, which also means no upload limits and no privacy worries.

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