The most important add-on.

My first add on on every fresh computer install

I've been using this extension for years. There are so many third party scripts that are completely unnecessary for the functioning of most websites that I browse. This extension allows me to control whose code runs on my computer. Try it out!

There are various add-ons that do affect security and privacy in a positive way, but I think this is the gold standard. Granted, it's intensive upon the user to allow and not allow exactly what they want to run which can frustrate the average user. But for anyone security-minded that is willing to put in the work, this is the best option you can have.