I've written a lot about converting different media types lately, especially GIFs, including Convert Video to GIF or GIF to Video, Detect if a GIF is Animated, and Get the First Frame of an Animated GIF with ImageMagick, but whether it's ImageMagick or ffmpeg doing the work, GIFs do not always come out optimized. Since GIFs can be taxing on the user's machine, it's best to optimize GIFs for top performance. Another handy GIF manipulation library, gifsicle, has a few built in methods for optimizing GIFs.
Before jumping into the GIF optimization commands, it's important to point out that gifsicle is much more than a GIF optimizer. gifsicle can resize GIFs, merge GIFs, and do just about anything you'd hope you could do with a GIF.
gifsicle has three types of GIF optimization to choose from:
-O1Stores only the changed portion of each image. This is the default.
-O2Also uses transparency to shrink the file further.
-O3Try several optimization methods (usually slower, sometimes better results).
The shell command to optimize GIFs is:
gifsicle -O3 animation.gif -o animation-optimized.gif
If you have the time and patience, I recommend
-O3 as was able to get much more optimized GIFs with this method. On some GIFs I saved up to 20% in file size, and depending on your specific GIF, you may be able to save more!