A video speed changer that runs in your browser
This video speed changer makes any clip faster or slower — from a quarter of normal speed to four times as fast — without uploading it anywhere. Pick a preset such as 2× or 0.5×, or type an exact value like 1.35×, choose what should happen to the sound, and download the result as an MP4. Decoding, retiming and encoding all happen on your own device using the browser’s WebCodecs video engine.
It is built for everyday jobs: speeding up a long screen recording so a tutorial gets to the point, slowing down a dance move or a golf swing to study it, turning a 3-minute walk-through into a 90-second social clip, or fixing a video that was recorded at the wrong speed. Unlike a player’s playback-speed button, the change is saved into the file, so it plays at the new speed everywhere you share it.
Two things set it apart. Voices stay natural, because the default audio mode time-stretches the sound instead of making it squeaky. And when the result can be played at its new frame rate, the video frames are copied without being re-encoded at all — so the picture quality is exactly the original and even long clips finish in seconds.
How to use the Video Speed Changer
- Drop a video onto the box or click to choose one. Its duration, resolution, frame rate and codecs appear, with the original in the Before player.
- Choose a Speed preset, or type any value from 0.25 to 4 in Custom speed. The note below shows the new length straight away.
- Pick the Audio mode: keep the pitch, let the pitch follow the speed, or mute the sound.
- Leave Frames on Auto unless you need a particular frame rate, and lower the Output size if you want a smaller, faster export.
- Press Change speed. Watch the progress bar (you can cancel at any time), compare the result in the After player and press Download MP4.
Video Speed Changer features
Any speed from 0.25× to 4×
Eight one-tap presets plus a custom field in 0.05 steps, with the new duration calculated before you start.
Natural-sounding audio
A WSOLA time-stretch (waveform-similarity overlap-add) keeps voices at their normal pitch; or let the pitch rise and fall with the speed, or mute the track.
Lossless when possible
For H.264 and HEVC videos whose new frame rate stays between 12 and 60 fps, the encoded frames are copied with new timestamps, so the picture is untouched and processing takes seconds.
Clean re-encoding when needed
For extreme speeds the video is decoded and rebuilt at a steady frame rate — frames are dropped evenly when faster and repeated when slower.
Before and after preview
Play the original and the result side by side before downloading, with the new length, size and frame rate listed.
Private by design
Videos are processed in memory on your device and never uploaded. Only the open-source Mediabunny library (MPL-2.0) is downloaded from a CDN.
Speed, duration and frame rate
The new length is simply the old length divided by the speed: a 3-minute clip at 1.5× lasts 2 minutes, and at 0.5× it lasts 6 minutes. What happens to the frames depends on the Frames setting. With Keep every frame, every original frame is kept and shown for a shorter or longer time, so the frame rate is multiplied by the speed. With a fixed rate, the tool samples the original at regular steps instead.
| Source | Speed | Keep every frame | Source frame rate |
|---|---|---|---|
| 30 fps | 2× | 60 fps, all frames | 30 fps, every 2nd frame |
| 30 fps | 4× | 120 fps, all frames | 30 fps, every 4th frame |
| 60 fps | 0.5× | 30 fps, all frames | 60 fps, each frame shown twice |
| 24 fps | 0.25× | 6 fps, all frames | 24 fps, each frame shown 4 times |
Which audio mode should you use?
- Keep pitch (time-stretch) — best for speech, tutorials and vlogs. The sound is cut into 40 ms overlapping slices that are realigned where the waveforms match, so the voice keeps its tone. Above about 2.5× or below 0.5× some echo or warble becomes audible; that is normal for any time-stretch.
- Pitch follows speed — the classic tape effect: 2× sounds an octave higher, 0.5× an octave lower. A proper anti-aliasing filter is applied, so fast versions do not crackle.
- Mute — removes the audio track, which also makes the file a little smaller. Good for background footage you will set to music later; you can extract the original sound first with Video to Audio.
Related edits
For dramatic slow motion of one moment, with smooth ramps in and out, use Slow Motion Video. To compress hours into seconds, the Time-Lapse Maker samples frames at up to 100×. To turn a sped-up moment into a loop for chat, try Video to GIF.
Video Speed Changer FAQ
How do I speed up a video without changing the voice?
Choose the speed, keep Audio on “Keep pitch (time-stretch)” and press Change speed. The tool shortens the sound without raising its pitch, so people still sound like themselves at 1.5× or 2×.
Is this video speed changer free and private?
Yes. There is no sign-up, watermark or upload. The video is decoded and encoded by your browser on your device; it never leaves your computer or phone.
Will changing the speed reduce the quality?
Not when the frames can be kept: then the original encoded frames are copied unchanged. At extreme speeds, or when you choose a fixed frame rate or smaller size, the video is re-encoded at high quality, which is visually very close to the original.
Why does my 0.25× video look jerky?
Slowing down does not create new movement — a 30 fps clip at 0.25× has only 7.5 real frames per second. For smoother slow motion, film at 120 or 240 fps, or use Slow Motion Video, which can blend neighbouring frames.
What is the longest video I can use?
Files up to 2 GB work, and the result can be up to 20 minutes long. Long, high-resolution exports need plenty of memory; choose 720p or 1080p output to make them faster and lighter.
Which formats are supported?
MP4, MOV, WebM and MKV with H.264, HEVC (where the browser supports it), VP8, VP9 or AV1 video. The result is an MP4: re-encoded video uses H.264 with AAC audio where the browser offers them, and copied frames keep their original codec.