Changing a video's speed is useful for a wide range of purposes. Speeding up creates a time-lapse effect: a 10-minute cooking process becomes a 30-second montage. Slowing down turns everyday footage into dramatic slow motion, revealing details invisible at normal speed.
How speed changes work technically
When you speed up a video by 2x, the tool either drops every other frame (fast but lower quality) or adjusts the timestamps so frames display twice as fast (re-encode approach). The result is a video that plays in half the time.
When you slow down a video to 0.5x, the tool doubles the display time of each frame or interpolates new frames between existing ones. Basic tools duplicate frames, which can look stuttery. Advanced tools use motion interpolation to generate smooth in-between frames, but this requires significantly more processing power.
For browser-based tools using FFmpeg, the standard approach is timestamp adjustment with frame duplication or dropping. The results are good for common speed factors like 0.5x, 1.5x, and 2x.
What happens to the audio
Audio speed changes are the trickiest part. Simply playing audio faster raises the pitch (chipmunk effect). Playing it slower lowers the pitch (deep voice effect). Neither sounds natural.
Good tools apply pitch correction so the audio stays at its natural pitch even when the speed changes. This uses a technique called time-stretching, which adjusts the tempo without altering the frequency. The MediaBrew speed tool applies pitch correction automatically, so a 2x sped-up tutorial still sounds natural.
At extreme speeds (4x or 0.25x), even pitch-corrected audio becomes hard to understand. For very fast speeds, consider muting the audio entirely and adding music or a voiceover afterward.
Common speed settings and their uses
0.25x gives a dramatic slow-motion effect. Good for sports replays, nature footage, or highlighting fast movements. 0.5x is a gentle slow motion that still feels watchable. 1.5x is a subtle speedup that makes tutorials and presentations feel brisk without losing comprehension. 2x is the standard fast-forward speed. Good for time-lapses and condensing longer footage. 4x creates a very fast time-lapse, best used without audio.
How to change video speed in your browser
The MediaBrew speed tool lets you upload any video and choose from preset speed options (0.25x, 0.5x, 0.75x, 1.5x, 2x, 4x) or enter a custom value. Audio pitch is corrected automatically. The process runs entirely in your browser using FFmpeg WebAssembly. No upload, no account, and no watermark.