Firefox previously had an Enhanced Tracking Protection feature that had one fatal flaw: it worked on a blacklist system, which meant that trackers and attackers that are not on that list would still be able to do harm. In contrast, Total Cookie Protection applies to any and all cookies, so there’s really no escaping it. At the same time, however, websites won’t suddenly stop working properly just because this feature is enabled.
What this new technology does is sandbox each website with its own cookie jar, and these websites can’t reach into other websites’ spaces and read cookies stored there. The old cookie system had a single big jar for all cookies, and websites could track you across the different websites you visit. The site’s cookies will still exist, and they will be able to perform their legitimate functions, including sending analytics back to the site owner for improving the service, at least if you give the site permission to.
The concept might sound pretty basic, but what made Mozilla dare to claim the title of the safest major desktop browser is how it is rolling out the feature. Total Cookie Protection is being turned on by default on Windows, Mac, and Linux, unlike similar features on other browsers that are opt-in. That said, this new feature is available only on Firefox for the desktop, so that protection and claim don’t extend to smartphones and tablets where a lot of people do their web browsing these days.