The feature is meant to prevent sites from tracking your browsing history.

Out of all of the major internet browser options, Mozilla’s Firefox places the greatest emphasis on privacy features intended to keep user information private and inaccessible by third parties. Today, Mozilla has touched up one of Firefox’s features, anti-tracking, overhauling into a new feature called “Total Cookie Protection.”

Total Cookie Protection prevents websites from accessing cookies stored on a user’s browser placed by other sites. Normally, all websites would be able to access this shared pool of local data, which in turn would allow those sites to see a user’s recent browser history. This kind of information is usually skimmed for marketing purposes. With Total Cookie Protection, one site won’t be able to read the cookies placed by another.

Mozilla explained the system on their blog, using a cookie jar as a metaphor. “Any time a website, or third-party content embedded in a website, deposits a cookie in your browser, that cookie is confined to the cookie jar assigned to only that website. No other websites can reach into the cookie jars that don’t belong to them and find out what the other websites’ cookies know about you … This approach strikes the balance between eliminating the worst privacy properties of third-party cookies – in particular the ability to track you – and allowing those cookies to fulfill their less invasive use cases (e.g. to provide accurate analytics).”

Mozilla hopes this and other privacy features will give users greater control over who can see their data and what it’s being used for. “Internet users today are stuck in a vicious cycle in which their data is collected without their knowledge, sold, and used to manipulate them,” Mozilla’s chief security officer Marshall Erwin told The Verge. “Total Cookie Protection breaks that cycle, putting people first, protecting their privacy, giving them a choice and cutting off Big Tech from the data it vacuums up every day. The feature offers Firefox’s strongest privacy protection to date and is the culmination of years of work to clamp down on online tracking.”