Gifsicle twaddles GIF image files in a variety of ways. It is better
than many of the freely available GIF twaddlers on the market -- for
one thing, it has more options.

It supports merging several GIFs into a GIF animation; exploding an
animation into its component frames; changing individual frames in an
animation; turning interlacing on and off; adding transparency; adding
delays, disposals, and looping to animations; adding or removing
comments; flipping and rotation; optimizing animations for space; and
changing images' colormaps, among other things. Extensive command-line
options control which, if any, of these occur.

Gifview, a companion program requiring X11, displays GIF images and
animations on an X display. It can display multi-frame GIFs either as
slideshows, displaying one frame at a time, or as real-time animations.

Gifdiff, another companion program, checks two GIF files for identical
visual appearance. This is probably most useful for testing
GIF-manipulating software.