Change Video Speed
Create dramatic slow-motion effects or speed up long footage with our free video speed changer. Adjust playback from 0.25x ultra-slow to 8x fast-forward — audio pitch adjusts automatically.
No account, no login, no credit card — just open and use.
How It Works
Upload your video file
Choose your desired playback speed
Process and download the result
Features
Use Cases
Create slow-motion replays for sports clips
Speed up tutorials and time-lapse footage
Match video duration to music tracks
How the speed change works
Two filters run in lockstep. On the video side, setpts rescales every frame's presentation timestamp — at 2x each frame is told to display in half the time. On the audio side, atempo time-stretches the waveform so it keeps pace without shifting pitch. Because both operate on the same factor, lips stay in sync with voices at any speed from 0.25x to 8x.
Everything runs locally in your browser through FFmpeg compiled to WebAssembly. Your footage is never uploaded; the cost is that your own machine does the encoding, so a long 4K file at 0.25x — which quadruples the frame count — will make the fan spin.
Choosing a speed that works
Small changes read as pacing, not effect: 1.25x–1.5x tightens screen recordings, lectures and tutorials while keeping speech intelligible. 2x is the practical limit for listenable voice. Above that, treat the result as time-lapse — great for unboxings, drives, cooking prep and long processes where nobody needs the audio.
Going down, 0.5x reads as deliberate slow motion and works on ordinary 30 fps footage. Push to 0.25x only if the source was shot at a high frame rate, or accept a visible frame-step. For a sports highlight, try trimming to the key two seconds first, then slowing just that clip — the contrast against full-speed footage is what sells the moment.
Frequently Asked Questions
Does changing speed alter the audio pitch?
No — the audio is time-stretched, not resampled. The tool uses FFmpeg's atempo filter, which changes tempo while preserving pitch, so voices stay natural instead of turning into chipmunks when sped up or slowing into a growl. If you actually want the cartoon effect, that is what the Voice Changer tool is for.
What speed range is supported?
0.25x (quarter speed) up to 8x (eight times faster). For extreme values the audio filter is chained automatically — atempo works in steps between 0.5x and 2x, so a 8x change applies 2x three times behind the scenes. You just pick the number.
Will slow motion look smooth?
Slowing down redistributes the frames you already have: a 30 fps clip at 0.25x plays back the equivalent of 7.5 fps, so very slow speeds can look steppy. Footage shot at 60 fps or higher slows down much more gracefully. Speeding up has no such limit — frames are dropped, not invented.
Is the video re-encoded?
Yes — changing playback timing requires rewriting every frame's timestamp, so the video is re-encoded with H.264 at quality level CRF 23 and audio at AAC 192 kbps. That is visually transparent for most footage, but unlike trimming, processing time scales with video length.
Does the video length change?
Yes, proportionally: a 10-minute video at 2x becomes 5 minutes; at 0.5x it becomes 20 minutes. Plan for the longer output when slowing down large files, since the encoder has to write every one of those extra frames.
Often Used Together
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Open Change Video Speed Tool — FreeNo sign-up • No installation • Works on any device