Description:

Gifsicle is a command-line tool for creating, editing, and getting
information about GIF images and animations.

Some more gifsicle features:

* Batch mode for changing GIFs in place.
* Prints detailed information about GIFs, including comments.
* Control over interlacing, comments, looping, transparency...
* Creates well-behaved GIFs: removes redundant colors, only uses local
color tables if it absolutely has to (local color tables waste space
and can cause viewing artifacts), etc.
* It can shrink colormaps and change images to use the Web-safe palette
(or any colormap you choose).
* It can optimize your animations! This stores only the changed portion
of each frame, and can radically shrink your GIFs. You can also use
transparency to make them even smaller. Gifsicle?s optimizer is pretty
powerful, and usually reduces animations to within a couple bytes of
the best commercial optimizers.
* Unoptimizing animations, which makes them easier to edit.
* A dumb-ass name.

One other program is included with gifsicle
and gifdiff compares two GIFs for identical visual appearance.