What actually makes a GIF big
GIF size is driven by pixels × frames × change. A 480×270 GIF with 100 frames holds 13 million pixels of image data; LZW compression shrinks runs of identical pixels but can’t do much with noise, film grain or dithering. Frame diffing helps a lot: when only part of the picture moves, only those pixels need storing. Lossy diffing goes further by treating “almost the same” pixels as unchanged.
Presets combine these levers: Light (256 colours, tiny lossiness) is visually transparent; Balanced (128 colours) suits most GIFs; Strong (64 colours, every 2nd frame, 75% scale) targets hard limits such as Discord’s 10 MB uploads. Some GIFs are already heavily optimised — then only resizing or trimming brings big gains.
When to stop compressing and switch format
If a GIF is still too large after Strong compression, the format itself is the bottleneck. Where video is allowed, GIF to MP4 is typically 5–10× smaller at better quality. Where a still image will do, GIF to PNG or GIF to AVIF are much smaller. Check any GIF’s platform limits with the GIF Tester.