Mozilla introduced a new privacy feature in Firefox 86 that stops cookies from being shared between websites. Mozilla calls it “Total Cookie Protection,” and it works by creating separate “cookie jars” for each website that you visit. By utilizing this cookie jar system, Firefox makes it so websites can’t track you across the web.
Total Cookie Protection is built into Firefox’s ETP Strict Mode. Mozilla describes it in a blog post:
Our new feature, Total Cookie Protection, works by maintaining a separate “cookie jar” for each website you visit. 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 that website, such that it is not allowed to be shared with any other website.
Firefox doesn’t just block every single cross-site cookie, though. Mozilla cleverly created exceptions for when you need cookies for non-tracking purposes, including third-party login providers. The browser can detect when you want to use a login provider and then specifically allow it for a site you’re on.
This setup means that your browsing experience shouldn’t be hampered but that cookies you don’t want tracked across sites will be isolated within their respective cookie jars.
The new Total Cookie Protection feature, when used in conjunction with Firefox’s Supercookie Protections should improve your browsing privacy significantly. Total Cookie Protection isn’t turned on by default, but you can easily switch it on.
There are also extensions to block cookies, but this new feature is baked right into Firefox.