Video Speed Changer
Speed a video up or slow it down, from 0.25× to 4×, with or without sound.
About this tool
Choose a speed from 0.25× to 4×, decide whether to keep the sound, and re-encode: the browser plays the video at that rate while recording. The output takes as long as the new length. Nothing is uploaded.
What speed changes do to sound and motion
Speeding up is the easy direction: a 4× time-lapse of a sunset or a 2× run through a lecture just drops frames the eye doesn't miss. Sound is the catch — the browser changes playback rate without time-stretching, so voices rise in pitch when faster and drop when slower (the chipmunk and slowed-down effects), which is why muting is offered and recommended beyond 2× or below 0.5×; the audio speed tool does the same to sound alone. Slowing down has a physical limit: a 30 fps clip at 0.25× shows each captured frame four times, which is smooth enough to study a golf swing or a dance step but not the buttery slow motion of a 240 fps camera, because those frames were never recorded. All processing runs on your device in real time at the output length — a 2× version of a four-minute video takes two minutes, a 0.5× version eight — and comes out as WebM (MP4 conversion where supported). Trim to the interesting part first.
Frequently asked questions
Will the voice sound like a chipmunk?
Yes at higher speeds — pitch follows speed here, honestly stated. Tick 'remove the sound' for big changes, or keep it at 1.5× where speech stays intelligible.
How slow can it go?
0.25×. Motion smoothness is limited by the frames the camera captured — slowed 30 fps footage looks stepped, not silky. That's physics, not the tool.
How long does it take?
As long as the OUTPUT plays: a 4× time-lapse of a minute takes 15 seconds; a 0.25× slow-motion of a minute takes four minutes.
Is the video uploaded?
No — playback and recording happen in your browser.