Retiring old GIF assets
A lot of GIFs are simply old — clip art, icons, buttons, and diagrams from sites and documents built long before WebP existed. As a still-image container GIF is inefficient: a 1987 design with a 256-color palette and compression that struggles with anything photographic. WebP replaces it comfortably for stills, storing full color in a smaller file, and every browser in current use displays it. Transparency comes along too, so a GIF icon with a see-through background stays see-through.
The animation is left behind
This page produces one still image per file. Drop in an animated GIF and you get a WebP of its first frame; the other frames are discarded. That is often exactly what someone wants — a thumbnail, or a static version of a moving graphic — but it is worth knowing before you convert a folder. If your goal is animation rather than a still, this is the wrong tool: the MP4 to GIF converter on this site is the one that produces moving output.
The colors do not come back
One limitation here is inherited rather than introduced. Your GIF has already been reduced to at most 256 colors, and converting it to WebP cannot restore shades the palette never held — banding in a photographic GIF stays banded. What you gain is a smaller, more modern file, not a repaired one. Everything runs locally in a Web Worker: three images convert at a time, each showing its original and new size, and they download one at a time or as a ZIP. No upload, no account, and no limit on the number of files.