What is Video Speed Changer?

Video Speed Changer adjusts your video playback speed — create slow-motion effects or speed up long recordings. All processing runs locally with ffmpeg.wasm, so your videos stay private. Slow a tutorial down to study it, or pack a long timelapse into a few seconds.

Speed presets stretch from 0.25× (cinematic slow motion) through 0.5×, 0.75×, 1×, 1.5×, 2×, 4× up to 8× (long surveillance review or extreme time-lapse). A three-way audio control lets you keep the original pitch, shift it with the tempo for a chipmunk effect, or strip the audio entirely. Type a target duration in seconds and the speed multiplier is computed for you. All processing runs in-page so private footage stays on your device.

How to use

1. Upload the video you want to adjust the speed of
2. Set the speed multiplier (0.25× for slow motion up to 8× for time-lapse) or type a target duration in seconds
3. Choose whether to preserve audio pitch, then process and download

When to use

• Turning a 10-minute window-cleaning session into a 2-minute satisfying timelapse.
• Slowing a golf swing to 0.25× to study form for sports coaching feedback.
• Tightening a wordy tutorial to 1.5× so listeners hit the punchline sooner.

Result

You have a 20-minute cooking tutorial and want a 5-minute timelapse version. Upload the video, set speed to 4×, and download the sped-up clip that shows the whole recipe in fast-forward.

FAQ

Will speeding up the video make voices sound like chipmunks?

Only if you pick the Change pitch audio mode. Keep pitch (the default) holds the voice at its normal tone even at 2× or 8×; the speech just speeds up. Pick Change pitch on purpose for the classic chipmunk effect, or Mute to remove the audio entirely.

How extreme can the slow motion get?

The minimum is 0.25× (quarter speed). True high-frame-rate slow motion needs the original footage to be recorded at 60, 120 or 240 fps. If the source is 30 fps, going to 0.25× makes each frame visible for 4 times longer, which can look stuttery on detailed motion.

Why does my fast-forwarded clip end up shorter in size but not by 4×?

A 4× speed-up means the file plays in a quarter of the original duration, but the visual content per second stays similar. The codec still has to describe each remaining frame, so the file does not necessarily shrink by exactly the same factor.

Can I apply different speeds to different parts of one video?

Not in this tool. Each pass uses a single speed multiplier. To create varying speeds, split the clip into segments using a trimmer, run each one through here at the speed you want, and re-join them in any video editor.

Does slowing the video also lower the frame rate?

No. The same frames are kept; each one simply lingers on screen longer. The output file therefore reports the same FPS as the source. To create true smooth slow motion, you would need extra frames generated by motion interpolation, which is beyond this tool's scope.

Related Tools