Change video speed

Speeding a clip up is straightforward. Slowing it down only looks smooth if the original was filmed with that in mind, otherwise the motion starts to judder. The sound can be corrected as it goes so voices still sound normal rather than chipmunk high or slurred.

How to use it

1 Add the video.
2 Choose a speed, or say how long it should end up and let it work the speed out.
3 Decide whether voices are kept sounding normal, left to change, or dropped entirely.
4 Encode and download.

Formats this tool accepts

Each one has a reference page covering what it stores and where it is supported.

Questions about change video speed

Will slow motion look smooth?

Only if the footage was recorded at a high frame rate. Slowing 30 frames per second footage to a quarter speed gives you an effective 7.5 frames per second, which judders. Footage shot at 120 or 240 frames per second slows down cleanly.

Does the audio go chipmunky?

Not with pitch correction enabled, which time-stretches the audio while holding the pitch. Turning it off gives the classic raised or lowered pitch, which is sometimes exactly what you want.

Does speeding up make the file smaller?

Usually, because there is less material to encode, though fast motion is harder to compress so the saving is less than the speed multiplier suggests.

Are my files uploaded to a server?

No. The whole thing runs inside the browser tab you already have open. Your file is read straight from your own disk, worked on there, and handed back as a download. Nothing is sent anywhere, nothing is stored, and there is no account and no queue.

Is there a file size limit?

There is no server-side limit because there is no server. The practical ceiling is your device memory, since the file and its output both have to fit in the tab. Files up to a few hundred megabytes are usually fine on a desktop machine, while phones and older laptops will struggle sooner. If a large file fails, close other tabs and try again.

Does it work offline?

Yes, once the page has loaded once. The engine is cached by the browser, so you can turn off your connection, reload the page and keep working. That is a useful side effect of doing the processing locally rather than a separate offline mode you have to enable.