Video Speed Changer — Slow-Mo & Fast-Forward in Browser
Change the speed of a video — 0.5× slow motion up to 2× fast-forward — with the audio tempo adjusted so it stays in sync.
Video Speed Changer
0.5× slow motion to 2× fast-forward
First run downloads the local engine (~31 MB) once, then your browser caches it for next time. Processing speed depends on your device — short clips are quickest, and longer videos simply take longer. Everything happens in this tab; the network stays empty the whole time.
How to change video speed in your browser
- Choose the video you want to retime.
- Pick a speed: 0.5× or 0.75× for slow motion, 1.5× or 2× for fast-forward.
- Run it. The frames are retimed and, if the clip has sound, the audio tempo is adjusted by the same factor so it stays in sync instead of stretching into a warble.
- Preview and download the result.
A 2× pass is the classic way to make a "here is my workday" or a long screen demo watchable; 0.5× is how a fast moment becomes slow motion. Both directions keep picture and sound aligned, and both happen on your device.
Why it's private
Speed-changing a video in the browser means your footage — often a recording of your own screen or work — never transits a third-party server. The retiming and the audio tempo change are computed locally by the ffmpeg engine in your tab.
Who needs this
Making a long screen recording watchable at 2×, or turning a fast moment into slow motion at 0.5× — with the audio staying in sync.