I'm not seeing animated images or videos on my Chromebook / Chrome OS

You may need to install "Proprietary Media Components" on your Chromebook.

To do that, go to your Settings by pressing on the right-bottom corner (time), and then on the Settings icon (3rd button after "Sign Out"):

Open the "Media Plugins" tab, and press the Install button for "Proprietary Media Components":

Restart your device after installing. Animated GIFs and Videos should now work on SimilarWorlds.