Video Speed
Speed up or slow down 0.25x-4x with pitch-preserving audio
Drag & drop files here
or browse files
Speed up or slow down a video with synced audio
About this tool
Turning a two-hour meeting recording into a 30-minute recap, stretching a three-second fail into a 0.5x replay, or shipping a 1.5x digest of a tutorial - speed changes are among the most common edits there are. This tool accepts any factor from 0.25x to 4x (six presets plus custom) and shows the resulting duration before you start.
Keeping audio in sync is the hard part: video timestamps are rescaled with setpts while the soundtrack runs through an atempo filter chain - a professional time-stretch algorithm that changes speed without changing pitch, so 2x does not sound like chipmunks and 0.5x does not slur. Factors above 2x automatically chain multiple atempo stages to keep each one in its optimal range.
Speed changes re-encode at high-quality CRF 20, entirely in your browser with nothing uploaded. Sped-up videos usually end up smaller; pair with the Video Compressor if you need more savings.
Features
- Any factor from 0.25x to 4x - six presets plus custom input
- Synced audio via atempo time-stretching: speed changes without pitch shift
- Live estimate of the output duration before you commit
- CRF 20 high-quality re-encode with AAC audio, universal MP4 output
- Fully local processing - no upload, no watermark, no limits
How to use
- Drop the video in - the original duration is read automatically
- Pick a preset or type a custom factor and check the estimated output length
- Click Change speed and wait for the re-encode
- Preview the result and download the MP4
Frequently asked questions
- Why does the audio not sound like chipmunks at 2x?
- The soundtrack goes through atempo, a time-stretching filter that changes playback speed while preserving pitch. Above 2x the tool chains multiple atempo stages (4x = 2x times 2x) so each stage stays in its optimal quality range.
- What happens to quality and file size?
- Frames are re-encoded at CRF 20, visually close to the source. Faster videos get shorter and usually much smaller; slower videos get longer and bigger - run them through the Video Compressor afterwards if needed.
- Can I change speed for only part of a video?
- This version applies one factor to the whole clip. The workaround is a three-step flow: cut the segment with the Video Trimmer, speed it here, then rejoin everything with the Video Merge tool.
- Which formats work, and is my video uploaded?
- MP4, MOV, MKV, AVI, WebM and other common videos, output as MP4. Nothing is uploaded - processing happens in your browser memory after a one-time ~31 MB engine download that is cached for offline use.