Did you know that invisible third party trackers monitor your online activity? This is done through the use of cookies, a small piece of data that is loaded every time you visit a particular site. Publicly, trackers are used to aggregate advertising metrics, like how long you watched a video, how many links you clicked on a page, how long you stayed on a site.  

Why is this an issue? Over time and repeated visits, a third party tracker is able to piece together a detailed story of your online behaviors. To stop third party trackers from invading your privacy, you can install the Privacy Badger browser extension developed by the Electronic Frontier Foundation. This extension monitors cookies and other content loaded on the sites you visit and blocks them when they exhibit tracker behavior.  

More about Privacy Badger from the EFF site

Install Privacy Badger on Chrome

Install Privacy Badger on Firefox