Speed Up or Slow Down Video
0.25× to 4× with natural-sounding audio
To speed up a video, open it above, pick a speed from 0.25× (slow motion) to 4× (time-lapse) — 2× is preselected — and export. The audio is retimed without the chipmunk effect, so voices stay natural. You can also reverse short clips. It all happens on your device.
Open a video to start editing
Your files never leave your device
How to make a speed up video
Open the video
Choose the clip to retime.
Choose a speed
Pick 0.25× to 4×, or tick Play backwards for short clips.
Export
Render the new version.
How speed changes work
Speeding up drops the time between frames and slowing down stretches it; Fylo then resamples the output to a steady 30 frames per second so it plays smoothly everywhere. Audio is retimed with ffmpeg's atempo filter, which changes tempo without changing pitch — so a 1.5× lecture still sounds like the speaker, just faster.
Slow motion expectations
Slowing a normal 30 fps phone video to 0.25× repeats frames, so motion looks steppy compared with true high-frame-rate slow motion. For smooth slow motion, record at 120 or 240 fps on your phone first, then slow it down here.
Speed and file size
Speeding up a video shortens it, so a 2× export is roughly half the length and noticeably smaller — a simple way to fit a long screen recording within a messaging app's limit. Slowing down does the opposite. Combine speed with trimming to keep only the part worth watching.
| Speed | Effect | Good for |
|---|---|---|
| 0.25×–0.5× | Slow motion | Sports, action moments |
| 1.25×–1.5× | Slightly faster | Tutorials, lectures |
| 2×–4× | Time-lapse | Cooking, travel, crafts |
Frequently asked questions
Will the voice sound like a chipmunk?
No — audio pitch is preserved.
Can I reverse a video?
Yes, tick Play backwards. Reverse needs to hold every frame in memory, so keep it under 60 seconds.
Can I speed up only part?
Speed applies to the whole export at the moment.
Does it work with GIF output?
Yes — choose GIF in Export for a sped-up looping GIF.
Can I make a time-lapse from a long video?
Yes. Choose 4× for the fastest speed, and trim the clip first so the time-lapse covers only the interesting part. For even faster playback, export once at 4× and then speed up the result again.
Are my files uploaded to a server?
No. Speed Up Video runs entirely in your browser — your files are processed on your own device and never sent anywhere. Once the page has loaded, it even keeps working if your connection drops.
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