Change playback speed
Half-speed slow-mo to 4× fast-forward. Audio pitch is preserved.
drop a video here
or click to choose
About speed changes
This tool stretches or compresses the video time. The audio gets time-stretched the same way, so a 2× speed-up still has audible voices — just faster — rather than chipmunk pitch.
Extreme speeds (under 0.25× or over 4×) can produce audio artifacts. We chain multiple atempo filters internally to extend the range, but really slow / really fast speeds work better with no audio.
Picking a speed
The presets cover most of what people need: 0.5× for slow motion, 2× for trimming dead time out of a screen recording or a talk, 4× for a fast run-through, and 8× for a timelapse. Anything in between can be typed in.
One thing to understand about slow motion: slowing footage down does not create detail that was never recorded. A 30 fps clip at half speed is still 30 real frames stretched over twice the time, so it will look slightly stuttery. Genuinely smooth slow motion has to be shot at a high frame rate in the first place — 60, 120 or 240 fps — and then slowed down.
What happens to the sound
- Keep the pitch the same — the audio is time-stretched, so a 2× speed-up still sounds like a person talking quickly rather than a chipmunk. This is what you want for anything with speech in it.
- Let the pitch shift, like a tape — the old-fashioned behaviour, where faster means higher. Occasionally the effect you actually want.
- Remove the audio — for a timelapse, where sped-up sound is just noise.
Pitch preservation works by chaining audio filters, and at extremes — below about 0.25× or above 4× — that chain starts to introduce artefacts. If a heavily sped-up clip sounds watery, dropping the audio is usually the better answer.
FAQ
Does the file get uploaded anywhere?
No. Nothing is uploaded. Open your browser's network tab while you convert and you will see your file never leaves the page. Once the converter itself has downloaded, it keeps working on this device even with no connection.
What's the maximum file size?
Browser memory is the limit. WebAssembly caps at 2–4 GB per file. Most laptops handle 1080p videos under a gigabyte comfortably.
Why is it slow on my phone?
FFmpeg-WASM runs on your CPU, not hardware video encoders. Phones have less CPU, so encoding takes longer.
Can I cancel mid-encode?
Yes. The Cancel button terminates the worker immediately. You'll wait a few seconds the next time you start.