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Change Video Speed: Slow Motion or Fast

Make a video slower (down to a quarter speed) or faster (up to four times), with the sound kept in tune or removed. Presets for slow motion and timelapse. Nothing is uploaded.

Private · on device. Runs in your browser: your file is not uploaded. No sign-up.

MP4, MOV (iPhone), MKV, WebM, AVI or 3GP, up to 2 GB

How to change the speed of a video

  1. Choose the video and pick a speed: a preset or the slider.
  2. Press play on the preview to watch it at that speed.
  3. Keep the sound in tune or remove it, then save and download the MP4.

Only want part of it? Trim the video first. To change the speed of a song or voice note, use audio speed and pitch.

The engine behind this tool

Video and sound are processed by FFmpeg, the open-source engine behind most of the world's video software, compiled to run inside your browser as ffmpeg.wasm. It is downloaded from this site (about 31 MB) the first time you use a video or audio tool, and your browser keeps it for next time. FFmpeg and ffmpeg.wasm are free software, licensed under the GNU General Public License version 2 or later; their source code is at github.com/ffmpegwasm/ffmpeg.wasm.

Frequently asked questions

Is my video uploaded?

No. The new speed is made on your own device by FFmpeg running in this browser tab.

Does the sound go high-pitched when sped up?

No. With "Keep, in tune" the sound is stretched or squeezed in time with its pitch kept, so voices sound like themselves, just faster or slower. Choose "Remove" for a silent video.

Why is my slow motion a little jerky?

Slow motion shows each frame for longer; no frames are invented. A normal 30 frames-a-second video slowed to ½× plays at an effective 15 frames a second. For smooth slow motion, film at 60 or 120 frames a second (the "Slo-mo" mode on most phones) and slow that down.

How fast or slow can it go?

From 0.25× (four times longer) to 4× (a quarter of the length), in steps of 0.05.

Can I check the speed before saving?

Yes. The preview plays your video at the chosen speed in your browser, instantly, before anything is re-encoded.