Change video speed
Make a video faster or slower, with sound that stays at the right pitch. Done on this device, never uploaded.
- Nothing is uploaded
- Works offline after first visit
- Open source
- No watermark · limit is your device’s memory; phones hold less
Speeds a video up to 2×, 4× or 8× or slows it to 0.5× or 0.25×, keeps the pitch of the sound, and saves an MP4. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after one visit to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
How it works
- Drop one or more videos (MP4, MOV, WebM or MKV), or tap to pick them.
- Choose a speed: above 1× to speed up, below 1× to slow down.
- Change speed. Each video is re-encoded at the new speed into an MP4, with its sound stretched to match.
In your browser, not on a server
Mediabunny (MPL-2.0) decodes the video in your tab and gives every frame a new time; when speeding up, frames beyond 60 a second are dropped. The sound track is decoded by your browser and stretched with WSOLA, a method that overlaps short slices of sound so the pitch stays the same. Both are encoded again by your browser (WebCodecs) into an MP4, H.264 and AAC where available.
Compared with upload-based tools: Online speed changers upload the video to process it, cap free files, and often add a watermark or turn voices into chipmunks. Here the video stays on your device and the sound keeps its pitch.
Verify it yourself. Give the page a short while after one visit to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Is my video uploaded?
No. Your browser decodes the video, re-times every frame and encodes it again in this tab. There is no upload and no watermark.
Does the sound speed up too?
Yes, and it keeps its pitch: the sound is cut into tiny overlapping pieces that are laid down closer together or further apart, so a voice at 2× sounds quick, not squeaky. Tick Remove the sound for a silent result.
Will slow motion look smooth?
Each frame is shown for longer, so 0.5× of a 60 fps phone video plays at a smooth 30 fps. Slowing a 30 fps video a lot will look steppy, because no new frames are invented in between.
Why is my sped-up video not much smaller?
Speeding up keeps up to 60 frames a second and drops the rest, so a 4× video is roughly a quarter as long but has the same picture quality per second. To make it smaller as well, run it through Compress video.
More video and audio tools
Merge videos
Combine clips into a single video, in the order you choose. Done on this device, never uploaded.
Add audio to video
Put music or a voice-over on a video, or replace its sound. The picture is copied as it is, and nothing is uploaded.
Reverse video
Make a clip play backwards, for a rewind effect, a boomerang or a laugh. Done on this device, never uploaded.
Video to JPG
Turn a video into still images: a few good frames or every single one. Done on this device, never uploaded.
Popular conversions
Guides
- How to slow down or speed up a videoThis changes the saved file itself, not just how a player plays it back. Here is what actually works, including keeping the audio in tune.
- How to reverse a videoRewind effects are popular, but most phones have no reverse button. Here is where it exists, and a way to do it without installing an app.