Trim, shrink and caption an animated GIF
Everything happens on your device — the file is never sent anywhere. The biggest savings usually come from the scale and color sliders; dropping frames helps on long animations, and a lower color count is nearly free on flat-colored artwork but shows banding on photographs.
The GIF format has been carrying short looping animations around the internet since 1987, and it has outlived far more capable successors for one stubborn reason: it plays absolutely everywhere, with no player, no codec and no permission needed. A GIF stores each frame as a grid of indexes into a palette of at most 256 colors, together with a delay telling the viewer how long to hold that frame before moving on.
That palette is also why GIF files get large so quickly. Every frame carries its own picture, so a long animation is genuinely a stack of images, and the compression that holds it all together works by spotting repeated runs of identical pixels. Anything that makes the picture simpler — fewer colors, smaller dimensions, fewer frames — therefore pays off twice, first by storing less and then by compressing what remains far better.
Trimming is usually the first thing worth doing, because most animations carry a second or two at each end that nobody needs, and those frames cost exactly as much as the interesting ones. Captions are the other common job: text burned into the frames themselves travels with the file, which is precisely why reaction GIFs are captioned rather than described, and why the text needs an outline to stay readable over whatever is moving underneath it.