GIF Reverser

Playing a GIF backwards turns a pour into an un-pour and a fall into a leap; a boomerang plays it forwards and then backwards so the loop never jumps. This tool rebuilds the animation in reverse order and keeps every frame's delay, its transparency and the loop setting. It works on GIFs whose frames only redraw part of the picture: each frame is drawn completely before the order is turned around. Everything happens in your browser.

How to use this tool

1. Choose one or more animated GIFs.
2. Choose "Reversed" or "Boomerang".
3. Optionally change the looping.
4. Download the new GIF.

Formula

Reversed: frames n, n − 1, … 1 · Boomerang: frames 1 … n, then n − 1 … 2

Each frame keeps the delay it had, so a slow frame stays slow in the other direction. A boomerang does not repeat the first and last frames at the turning points, which keeps the motion smooth when it loops; its length is the original length plus the middle frames once more. Frames are rebuilt from the fully drawn pictures, with only the changed pixels stored after the first frame.

Example

A GIF of 10 frames at 50 ms (0.5 s): reversed it is still 10 frames and 0.5 s. As a boomerang it plays frames 1–10, then 9–2: 10 + 8 = 18 frames, 0.9 s per loop.