Change the speed of a video
Pick a speed from 0.25× to 4×: the new length is shown before you export, and the audio keeps its natural pitch or is removed. You get an MP4, and your video never leaves your device.
- From 0.25× to 4×
- Audio pitch preserved
- MP4 export
- 100% private
100% private — Everything is processed directly in your browser: your files, voice, and image are never sent to Chatzam's servers.
How do you speed up or slow down a video?
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Add your video
Drag your video file into the box or select it on your device.
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Choose the speed
Click 0.25×, 0.5×, 0.75×, 1.5×, 2×, 3× or 4×, or set a custom value: the new length appears instantly. Keep the sound or remove it.
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Export as MP4
Start the conversion, then download the video as an MP4 (H.264). A long video takes more time.
Fast motion or slow motion, without warped voices
From 0.25× to 4×
Buttons for the usual speeds and a custom setting, from strong slow motion to fast forward.
Natural sound
The audio follows the speed without the chipmunk voice: its pitch is preserved. You can also remove it.
Length calculated in advance
The new length is shown before export, so you can aim for the maximum length of a post, for example.
No upload
Processing runs in your browser with FFmpeg: your video stays on your device.
Working out the new length of a video
The new length is simply the original length divided by the speed. A 3-minute video at 2× lasts 1 min 30 s; at 1.5×, 10 minutes become 6 min 40 s; at 4×, a 20-minute time-lapse fits into 5 minutes. Slowing down does the opposite and makes the video longer: 1 minute at 0.5× lasts 2 minutes, 4 minutes at 0.25×, and 3 minutes at 0.75× turn into 4. To fit a video into an exact length, divide the original length by the target length: to bring 1 min 30 s down to 60 seconds, you need 90 ÷ 60 = 1.5×. The tool shows the new length before export, so you can check it before starting the conversion.
Sped-up audio without the chipmunk voice
When you speed up a recording the simple way, like a record spinning too fast, the pitch rises with the speed: at 2×, voices are an octave higher, hence the chipmunk effect. In slow motion it's the opposite, and voices become deep and dragging. Here, the audio is recalculated to follow the speed while keeping its original pitch: a sped-up voice stays recognizable, just faster. That's ideal for a tutorial, a lecture or a meeting you want to watch again more quickly. If the sound doesn't matter, for a time-lapse or a sports slow-mo for example, remove it in the tool; to remove the sound without changing the speed, use "Remove Audio From Video".
Getting smooth slow motion and waiting for the export
Slow motion looks smoother when the video was filmed at a high frame rate. A clip shot at 120 frames per second and slowed to 0.25× still has 30 different frames per second, which stays smooth; a 30 fps video slowed to 0.25× only has 7.5 different frames per second and looks choppy. On a phone, film at 60 fps or more if you plan to use slow motion. As for the export, the video is fully re-encoded to MP4 (H.264) in your browser: the longer and higher-resolution it is, the longer it takes. To save time, first keep only the useful part with "Cut / Trim Video", then shrink the result with "Compress Video" if needed.
Frequently Asked Questions
How do I speed up a video?
Add the video, choose 1.5×, 2×, 3× or 4× (or a custom value up to 4×), then export it as an MP4. The new length is shown before export.
How do I slow down a video?
Choose 0.75×, 0.5× or 0.25× (or a custom value from 0.25×): the video gets longer, with 1 minute at 0.5× becoming 2 minutes. The audio keeps its natural pitch, or can be removed.
How long is a video at 2× speed?
Half as long: divide the length by the speed. A 3-minute video lasts 1 min 30 s at 2×, and a 45-minute video lasts 22 min 30 s.
Does the sound get distorted when you speed up a video?
No, the pitch is preserved: voices are faster but not higher. You can also choose to remove the sound.
Is my video sent to a server?
No. Processing runs in your browser with FFmpeg; only the FFmpeg engine is downloaded. It's free and there's no sign-up.