Video Speed Changer
Speed up or slow down a video (0.5×–2×), with matching audio, in your browser. Free, private, no signup or upload.
About the Video Speed Changer
This free video speed changer makes a clip play faster or slower — from half speed for a slow-motion look to double speed for a quick fast-forward. The audio is sped up or slowed to match, keeping its pitch natural so voices do not sound distorted.
All processing runs in your browser using FFmpeg WebAssembly, so your video is never uploaded. The engine (about 30 MB) downloads from a CDN on first use and is cached, so the first run is the slow one. The output is a widely-compatible H.264 MP4 with a web-friendly yuv420p pixel format.
Slowing a video down does not add new frames, so extreme slow motion can look a little choppy depending on the source frame rate; moderate changes look smoothest. You can also drop the audio entirely if you only need the visual speed change. Videos up to 100 MB are supported.
How to Use the Video Speed Changer
- 1Choose a video file, up to 100 MB.
- 2Set the speed from 0.5× (slow motion) to 2× (fast forward).
- 3Keep the audio (pitch-corrected) or remove it.
- 4Click Change Speed, preview and download the result.
Frequently Asked Questions
Is my file uploaded to a server?
No. All processing runs in your browser using FFmpeg compiled to WebAssembly. Your file never leaves your device — only the converter engine is downloaded, once.
Why is the first run slow?
The first time you use any converter here, the browser downloads the FFmpeg core (about 30 MB) from a CDN and compiles it. It is then cached for the session, so later runs are much faster.
Does the audio stay in sync?
Yes. The audio is time-stretched to match the new video speed and its pitch is preserved, so voices sound natural rather than sped-up or slowed-down like tape.
Why does slow motion look choppy sometimes?
Slowing down spreads the existing frames over more time without creating new ones. If the source frame rate is low, big slowdowns can look stepped. Moderate changes stay smooth.
Is there a file size limit?
Yes, 100 MB per file. Because everything runs in your browser's memory, very large files can be slow or run out of memory. Trim long clips first if you hit the limit.