Change Video Speed · Slow Motion or Fast Forward
Speed a video up or slow it down, from 0.1x to 16x, with natural-sounding voices or a tape-style pitch change. MP4 and MOV change speed in seconds without re-encoding, so every frame stays exactly as it was.
How to change the speed of a video
- Drop a video onto the box above.
- Pick a speed, or type your own. The player above plays at that speed right away so you can hear how it will sound.
- Choose what happens to the sound, click Change speed and save the new video.
Instant mode keeps every frame
An MP4 or MOV file stores how long each frame is shown. Instant mode changes only those timings: at 2x every frame is shown half as long, at 0.5x twice as long. The frames themselves are copied byte for byte, so there is no quality loss and a multi-gigabyte video is done in seconds. Only the sound is processed again, because sound cannot simply be played faster without changing its pitch.
Subtitles are kept and retimed too. Timecode and camera metadata tracks are left out because their timing no longer matches; the recording date and location of the file stay.
The catch is the frame rate: a 30 fps video at 4x plays at 120 fps, and at 0.25x at 7.5 fps, which looks choppy. The tool tells you the resulting frame rate and suggests re-encoding when it would be too high or too low.
Real slow motion from your phone
Phones film slow motion at 120 or 240 frames per second. Slow such a video to 0.25x in instant mode and it plays at 30 or 60 fps: genuinely smooth slow motion with every real frame, no invented in-between frames and no re-encoding.
Re-encode mode
Re-encoding keeps the original frame rate: when speeding up it leaves frames out, when slowing down it shows frames longer. The result plays smoothly on every device and is often much smaller when sped up. It also works for WebM, MKV, AVI and other formats. iPhone HDR video is converted to standard colours.
Frequently asked questions
Can I change the speed without losing quality?
Yes, for MP4 and MOV in instant mode. Only the sound is processed again.
Will voices sound like chipmunks?
Only if you want them to. Keep pitch keeps voices natural; Change pitch makes them higher or deeper like a tape.
Is my video uploaded?
No. Everything runs in your browser tab on your own device.