How to use it
- Open an animated GIF.
- Choose a preset speed or type your own between 0.1 and 10. Above 1 is faster, below 1 is slower.
- Check the duration before and after, and the preview.
- Download the GIF.
How it works
A GIF stores a Graphic Control Extension before each frame, and the frame delay is two bytes in it, counted in hundredths of a second. The tool walks all blocks, finds those delay fields and writes new values: the effective delay divided by the speed, rounded, and not less than 2. Everything else in the file is copied byte for byte.
Worked example
Frames of 10, 20 and 6 hundredths (0.36 s per loop) at 2x become 5, 10 and 3 hundredths, a loop of 0.18 s.
Tips
- Slowing down is exact. Speeding up a GIF that is already fast may hit the 0.02 s floor.
- To change the frames themselves, use the GIF maker or split the GIF into frames.