Reverse, or bounce
Reversing plays the frames last to first. It is the whole joke in a lot of reaction GIFs, and it is genuinely useful for showing a process undone — a thing assembling rather than falling apart.
Bouncing plays forward then back, which hides the jump a loop makes when the last frame does not match the first. For anything that does not naturally return to its starting position, a bounce loops seamlessly where a plain loop stutters.
Timing runs backwards too
GIF stores a delay per frame, so reversing the order without reversing the delays produces an animation with its pauses in the wrong places. Both are reversed here, and a bounce doubles the frame count — so the file roughly doubles too.
Frequently asked questions
Does the file get bigger?
A plain reverse is the same size — the same frames in the opposite order. A bounce roughly doubles it, because every frame appears twice.
Why does my reversed GIF pause in odd places?
It should not — the per-frame delays are reversed along with the frames. If you reversed it in software that only reordered the frames, the pauses end up mirrored.
What is bounce for?
Seamless looping. When the last frame looks nothing like the first, a plain loop jumps; playing forward then back always returns to where it started.
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