I'm not the author, but I'm pretty sure GIFs start to inflate when you increase colour depth.

GIFs we see on social networks are typically captured from videos of real-life objects, places and people, so the source colour-depth is pretty high (to account for the necessary shades created by varying exposure to light in three dimensions) and thus even a poor-quality GIF is going to be quite big to represent the source media with any discernible accuracy.

Since that terminal sports very few colours, it can be saved with low colour-depth and thence remain very small, despite size and length.

Asciinema could also be a useful way to present the example.

https://asciinema.org/

It wouldn't be useful in this particular case because you wouldn't actually get to see the browser window (I guess you could curl it or something). But this is a really neat tool, I'll definitely be using it. Thanks for sharing!

http://i.imgur.com/5sReybQ.gif Same image -> 333kb. There are a few tricks that you can apply to reduce the size while keeping the same visible quality: http://ezgif.com/optimize

Gimp ;) (I know this doesn't answer your question, but it's the only answer I have O:-))

Run-length encoding FTW