Change video speed

Speed up or slow down a video from 0.25x to 4x in your browser. Nothing is uploaded and there is no server queue.

Drop your files here

.mp4, .mov, .mkv, .webm, .avi, .m4v · up to 200 MB

Choose files

How to Change speed

1
Add your video
Any MP4, MOV, MKV, WebM or AVI up to 200 MB and 5 minutes; speeds run from a quarter to four times the original.
2
Pick a speed
0.25x to 4x from the list, or type a custom value in between.
3
Click Apply and download
The new duration and frame rate are shown before you run it.

No frame is added or removed

Changing speed here is purely a matter of timing, not motion. Every frame the camera recorded stays in the file, in the same order. Only the moment each one is shown gets stretched or compressed. Doubling the speed means every frame is displayed for half as long; slowing to a quarter means each one lingers four times longer. Because the frame count never changes, the technical frame rate of the result, meaning what plays back per second, moves in exact proportion to the speed you pick: a 30 fps clip sped up 2x plays at an effective 60 fps, and slowed to 0.25x it plays at an effective 7.5 fps.

Why slow motion isn't always smooth

Slowing a video down doesn't invent frames that were never captured. A 30-frame-per-second source stretched to a quarter speed still only has 30 frames spread across four times the timeline, nowhere near the 120 frames a real high-speed camera would have shot for fluid slow motion. The result is watchable and useful for pacing or emphasis, but it won't look like footage from a dedicated slow-motion camera. There is no motion interpolation here to fill the gaps; that's a deliberate scope decision, the same one made for the frame rate tool.

Two ways to handle the audio

By default the audio is time-stretched to match the new length while its pitch stays where it was, so a 2x speed-up plays twice as fast without turning voices into chipmunks. Switching to 'linked pitch' instead resamples the audio the cheap way, letting the pitch rise with speed increases and drop with slow-downs. That's the classic effect used for comedic speed-ups or deliberately deepened, dragged-out narration, and it costs less to compute than true time-stretching.

File size follows the new frame rate

Because the encoder targets the effective frame rate rather than the original one, speeding a video up raises the bitrate and the output size, while slowing it down lowers both. A 2x speed-up of a busy 1080p clip typically produces a noticeably heavier file per second of playback than the same clip slowed to 0.5x, even though both started from the same source.

Retimed inside this tab

Frames are retimed and encoded again by your browser's own video codec, while a WebAssembly audio engine stretches the soundtrack and keeps its pitch unless you link the two. All of it happens on your device: nothing is uploaded, there is no queue, and closing the tab clears everything.

Frequently asked questions

Does the pitch of voices change?

Not by default. 'Preserve pitch' stretches the audio in time without shifting its tone, so speech and music sound natural at any speed. Switching to 'linked pitch' lets the tone rise or fall with the speed instead, on purpose.

Why doesn't slowing down make the video smoother?

The tool doesn't create new frames; it only shows the existing ones for longer. A source shot at 30 frames per second stays a 30-frame source no matter how much you slow it down, so true high-speed-camera smoothness isn't possible here.

What is 'linked pitch' and why would I want it?

It resamples the audio so pitch changes together with speed: higher and squeakier when sped up, lower and slower when slowed down. It's the classic cartoon or dramatic-slow-motion sound effect, and it's cheaper to compute than preserving pitch.

How is the new file size calculated?

The video bitrate is set from the effective frame rate, the original frame rate multiplied by the speed factor, so faster clips get a higher bitrate and slower clips get a lower one, matching the extra or reduced motion per second.

Can I set a speed that isn't in the list?

Yes. Pick 'Custom' and enter any value from 0.25x to 4x in steps of 0.05.

How is this different from the frame rate tool?

The frame rate tool changes how many frames play per second while keeping the total duration the same, by default. This tool does the opposite: it keeps every frame but changes how long the whole video plays for, which is exactly what a speed change means.