Retiming without re-encoding
Most speed changers re-encode every frame, which takes ages and softens the picture. This tool works differently: it rewrites the video's timing metadata, telling every frame to display sooner or later, while copying the encoded frames untouched. The result is mathematically identical picture quality, and because nothing is re-encoded, a speed change on a long video takes seconds, not minutes.
Everything runs in your browser. The file is never uploaded, which is why there is no size limit, no queue, and no cap on how many videos you process.
Slow motion, timelapse, and everything between
Use 0.25x or 0.5x to study sports technique, savor a pet's antics, or fake a slow-motion shot from regular footage; note that slowing down does not invent new frames, so very slow playback of low-frame-rate video looks steppy. Use 1.5x or 2x to tighten screen recordings and lectures, and 4x or the custom slider up to 8x to turn long footage into a timelapse. The custom slider goes down to 0.1x for extreme slow motion.
What happens to the audio
Audio cannot simply be retimed the way frames can; it has to be resampled. By default the output is silent, which suits timelapses and slow-motion clips where the sped-up audio would be noise anyway. Turn on Keep audio to resample the soundtrack to the new speed; like tape, the pitch shifts with it, chipmunk up, slow-motion down. For trimming before or after, use the free video trimmer, and to shrink the result, the free video compressor.