Change Video Speed
Upload a video and change its speed — processed locally with no upload to any server.
Playback Speed
Speed up
All processing happens in your browser — your files are never uploaded.
How to use Change Video Speed
The Video Speed tool lets you speed up or slow down an MP4, WebM or MOV video by adjusting the playback rate — from 0.25× for slow-motion to 4× for a fast-forward timelapse — and exports the re-encoded output entirely in your browser without any file uploads. Use it to create slow-motion replays, speed-ramp edits or condensed time-lapse clips from normal footage.
- Click "Select Video" and open your MP4, WebM or MOV file.
- Choose the playback speed multiplier (e.g. 0.5× for half speed, 2× for double speed).
- Decide whether to keep, stretch or remove the audio track to match the new duration.
- Preview the result at the selected speed to check it looks correct.
- Click Export and download the speed-adjusted video file.
Your data never leaves your device — 100% private processing.
Speed change and audio pitch
When a video is slowed down, audio pitch drops because fewer audio samples play per second. When sped up, pitch rises. Most video editors apply pitch correction to keep voices sounding natural at changed speeds — a technique called time-stretching. This tool can optionally pitch-correct the audio using a phase-vocoder algorithm so that dialogue remains intelligible even at 0.5× or 2× speed. Removing the audio entirely and adding a separate music track is another common approach for timelapse or highlight-reel videos.
Frame rate considerations for slow motion
Genuine slow motion requires high-frame-rate source footage — 60 fps slowed to 0.5× produces smooth 30 fps playback, while 30 fps footage slowed to 0.5× produces a choppy 15 fps result. If your source was shot at 30 fps and you slow it to 0.25×, the tool interpolates frames using optical-flow estimation to fill in the missing frames and reduce stuttering. For the best quality slow motion, record at 120 fps or 240 fps on a modern smartphone or mirrorless camera before applying the speed change here.
Glossary
- Time-stretch
- Changing the duration of an audio or video clip without affecting its pitch, using algorithms like phase-vocoder or WSOLA.
- Pitch correction
- Adjusting the pitch of audio after a speed change so that voices and instruments sound natural despite the tempo change.
- Frame interpolation
- Generating intermediate video frames between existing frames using motion estimation, used to smooth slow-motion output from low-fps source footage.
- Optical flow
- A computer-vision technique that estimates the motion of pixels between frames, used for frame interpolation and video stabilisation.
- Timelapse
- A video technique where footage is sped up significantly (e.g. 10×–100×) to compress long events like sunsets or construction into a short clip.
Related reading
Frequently Asked Questions
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Why use Change Video Speed?
- Powered by FFmpeg running directly in the browser — no upload needed
- Supports all major video and audio formats
- Lossless and lossy options for quality control
- Export results immediately without waiting for cloud processing
Common use cases
- Compress a video before uploading to Google Drive
- Extract audio from a video lecture for easy listening
- Trim a video clip for a social media reel
- Convert MOV files to MP4 for cross-platform compatibility
- Merge two audio tracks for a podcast episode
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