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Speed up

Speed up part of a video online

Make a video, or one boring stretch of it, play faster — 1.5x, 2x, 4x, 8x or any multiplier you type. The audio is retimed without going squeaky, and the whole thing runs in this tab, so your file is never uploaded.

Drop your video here

or click to browse — MP4, MKV, MOV, WebM, AVI and more

How to make a video faster in your browser

  1. 01

    Open your video

    Drag an MP4, MOV, MKV, WebM or AVI onto the drop zone above. It is opened straight off your disk — there is no upload step to sit through first.

  2. 02

    Mark the section to accelerate

    Right-click the timeline where the slow part begins and choose Speed up, or park the playhead there and press "+ Add edit". A green band marks the range.

  3. 03

    Choose a multiplier

    Pick 1.5x, 2x, 4x or 8x from the card, or type your own value between 1.1x and 16x. Below 1.1x the change is too small to be worth a re-encode, so the field will not go there.

  4. 04

    Speed up the whole clip if you want

    To accelerate everything, drag the band handles from 0 to the end of the timeline. There is no separate "whole video" mode because the range already covers it.

  5. 05

    Apply and download

    Press Apply All Edits. The editor shows an estimated output duration before you commit, and the download link appears when the encode finishes.

Picking a speed: what each multiplier is good for

1.5x

Tightening a talking-head recording. Fast enough to save real time, slow enough that nobody notices you did it.

2x

The default for cutting a demo or a tutorial down to size. Speech is still comfortably followable.

4x

Skimming past an install, a render or a long approach shot. Speech becomes hard to follow, so this is for footage you do not need to hear.

8x to 16x

Time-lapse territory: a long static shot compressed into a few seconds. Expect heavy frame dropping, and consider muting the audio entirely. 16x is the ceiling.

What FFmpeg does to speed a section up

The clip is split into three pieces: everything before the selection, the selection itself, and everything after it. Only the middle piece is retimed. Its video timestamps are divided by the multiplier with setpts=(PTS-STARTPTS)/factor — halving every timestamp is exactly what "play it twice as fast" means — and the three pieces are concatenated back into one stream.

Audio is handled separately by atempo, which resamples in a way that changes tempo without changing pitch. That is why sped-up speech here does not turn into a cartoon voice. atempo refuses factors above 2.0, so a 4x request becomes atempo=2.0,atempo=2.0 and an 8x request chains three of them — the editor builds that chain for you.

One thing worth knowing: this is timestamp retiming, not frame interpolation. Frames get dropped to fit the shorter duration, they are not blended into new ones. That is the correct behaviour for a time-lapse and the reason a heavily sped-up pan can look a little steppy. The full pipeline is documented here.

Speeding up and file size

A sped-up video is shorter, so it is almost always smaller — a 2x section contains half the play time and therefore roughly half the bits. If size is the actual goal, the max-resolution control does more: capping a 4K screen recording at 720p shrinks it far more than any speed change, and it makes the encode finish sooner too, since your CPU has a quarter of the pixels to compress.

If you only want the footage shorter and you do not care about the middle at all, a cut is cheaper than a speed-up: removing the section outright takes it to zero seconds instead of a fraction of them.

Speeding a passage up is also the tidiest way to bring a clip under a hard duration limit without losing anything: a section of length L at factor f becomes L/f, so thirty seconds at 1.5× saves ten. Trimming a video to a specific length works through that arithmetic against a target.

Questions about speeding up video

Can I speed up only part of a video?
Yes. A speed-up applies to the range you mark on the timeline, not to the whole file. Everything outside that range keeps playing at normal speed, so you can compress a slow middle section while leaving the intro and the ending alone.
Does speeding up the video make the audio sound like a chipmunk?
No. The audio is retimed with FFmpeg's atempo filter, which changes tempo without shifting pitch. Sped-up speech stays recognisable as the same voice, just faster. Above about 3x it starts to sound clipped, which is a limit of the technique rather than a bug.
What speed multipliers can I use?
There are presets for 1.5x, 2x, 4x and 8x, and you can type any custom value between 1.1x and 16x. atempo only accepts a factor up to 2.0 per instance, so higher multipliers are produced by chaining several atempo filters together automatically.
Does speeding up a video lose frames?
Yes, and that is expected. Speeding up rewrites presentation timestamps, so a 4x section plays four times as much source footage in the same wall-clock time and roughly three out of every four frames are dropped rather than blended. The result looks like a time-lapse, which is normally what you want.
Is the video uploaded to speed it up?
No. The retiming and the re-encode both happen in your browser tab through FFmpeg WebAssembly. No copy of the file is sent anywhere, so there is no upload wait and nothing to delete afterwards.

Other edits on the same timeline

The same timeline also lets you slow a section down and cut a section out, and you can combine all three in one pass. Start from the free online video editor if you want everything at once.

Guides on changing video speed

The mechanics behind the multiplier: what setpts and atempo do, why frames are dropped rather than blended, what it costs, and where to do it when the only machine to hand is a phone.

All video editing guides