Where GIF images are still required
GIF works in every browser and email program, including very old ones. Some older websites, forum signatures, email newsletter systems, intranets and small embedded screens still accept only GIF. Converting your pictures makes them usable in those places.
What happens when you convert
Each picture becomes one still GIF file. The colours are reduced to the best palette of up to 256 colours for that picture, transparent areas stay transparent, and pictures wider than 2000 pixels are scaled down to 2000 pixels wide. This tool does not combine pictures into an animation.
How the result will look
Logos, icons, buttons, cartoons and diagrams with flat colours look clean and sharp as GIF. Photos and smooth colour gradients lose quality because 256 colours are not enough — you may see banding or a grainy look.
Common problems and how to fix them
Photos look grainy: use JPG, PNG or WEBP instead unless GIF is required. Edges of a transparent logo look rough: GIF transparency is on or off per pixel, so soft edges become hard; put the logo on the background colour it will appear on. The file is too large: reduce the picture's width with Resize Image first.
Good habits
Use GIF only when a system requires it, keep the original high-quality files, and check the GIF on the background where it will be used.