It is called the tab throbber for some reason. I see you already discovered this thread and said you do not understand what is being said there: [https://support.mozilla.org/questions/1189487 Blue Dot Bouncing From Side To Side] To summarize: you can change that animation to another one, or hide it completely. That involves creating a file and pasting in some style rules. It takes 5-10 minutes to set that up the first time, but if you decide to paste other style rules into the file in the future, that obviously will go much faster. So it depends on how annoying this is to you, or how big your wish list for modifications is, whether it makes sense to start down this road. I made a video about userChrome.css on Macs if you have 5 minutes to kill: [https://vimeo.com/245560075 How to Set Up userChrome.css on Mac on Vimeo]