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Speed up or slow down a video

Pick a speed, preview the timing and sound, then create the synchronized video.

InputMP4, WebM, MOV and M4V videoOutputMP4 or WebM video

MP4 · WebM · MOV · M4VDrop a video to change its speedor click to choose a file.

Speeding a video up compresses dead time; slowing it down makes fast action readable. This tool re-times a clip anywhere between a quarter speed and four times speed, and re-times the soundtrack to match so the result stays synchronised rather than drifting further apart with every second of playback.

What speed does to motion

Speeding up drops frames, so a 60-second clip at 2× becomes 30 seconds of the same footage with half the frames retained. That is invisible for screen recordings and talking heads and slightly stuttery on fast pans. Slowing down has the opposite problem: there are not enough real frames to fill the extra time, so frames are held or blended and fast motion looks juddery. Genuinely smooth slow motion has to be recorded at a high frame rate in the first place — a 120 fps source slowed to a quarter still delivers 30 real frames per second, while a 30 fps source cannot.

What speed does to sound

Audio has to change with the picture or lip sync collapses. Sped-up speech rises in pitch and eventually turns comic; slowed speech drops and turns muddy. Around 1.25× to 1.5× most speech stays perfectly intelligible, which is why so many people watch lectures that way. Beyond about 2× it is worth asking whether you want the audio at all — for a timelapse or a build montage, muting and adding music is usually better than shipping a chipmunk voice.

Questions, answered

Does changing speed keep the audio in sync?

Yes. The soundtrack is re-timed with the picture rather than being left at its original rate, so sync holds from start to finish.

Why does my slowed-down video look choppy?

Because the source does not have enough frames to fill the longer duration. Smooth slow motion needs high frame rate footage — 60, 120 or 240 fps — recorded specifically for the purpose.

Will speeding up make the file smaller?

Usually yes, because the video is shorter. The saving is less than proportional, since a faster clip has more change between frames and compresses less efficiently per second.

What speed is best for a timelapse?

That depends on the source length; the practical range here tops out at 4×. For extreme timelapses, run the clip through more than once, or capture at a low frame rate to begin with.

Can I change speed for just part of a video?

The speed applies to the whole clip. For a speed ramp, split the video, process each part at its own speed, and merge the parts back together.

Speed up or slow down a video

What speed does to motion

What speed does to sound

Questions, answered

Useful next steps