The ongoing race between advertisers and users over persistent tracking across the web has a new entrant. With the latest release of its Firefox browser, Mozilla has introduced a feature that blocks cookies and storage access from third-party trackers.

The feature is known as Enhanced Tracking Protection and it’s enabled by default in Firefox 63, which Mozilla launched earlier this week. This is not just a newer version of the old Do Not Track signal, but rather a comprehensive method for addressing the problem of third-party trackers setting cookies on users’ machines. That’s the main way that trackers follow users across the web and much of that activity is invisible to users, unless they go looking for it. Even then, it’s difficult to understand exactly what the trackers do and how their presence affects users’ privacy over the long haul.

Firefox 63 takes the responsibility for figuring that stuff out off of users’ shoulders by blocking third-party trackers from advertisers, social media platforms, and others from the get-go. Mozilla has had a version of tracking protection in Firefox’s Private Mode for several years, but it sometimes caused sites to break or render in weird ways, so the company hadn’t added it to  the normal mode. The new feature is designed to address the breakage issues while still offering users advanced tracking protection.

“The desired outcomes are clear – people should not be tracked across websites by default and they shouldn’t be subjected to abusive practices or detrimental impacts to their online experience in the name of tracking. However, the challenge with many privacy features is that there are often trade-offs between stronger protections and negative impacts to user experience,” Peter Dolanjski, Firefox product lead at Mozilla, said in a post.

“Historically this trade-off has been handled by giving users privacy options that they can optionally enable. We know from our research that people want these protections but they don’t understand the threats or protection options enough to turn them on.”

Tracking protection is developing into one of the more important methods for browser makers to protect users as they move around the web. As ad blockers have proliferated and online ad revenue has deteriorated, companies have struggled to find new ways to get their messages in front of users. Tracking users across the web allows them to gather intelligence about users’ interests and movements, something that’s invaluable to advertisers. It’s also the lifeblood of some social media platforms, and the change in the way that Firefox handles those trackers makes life much simpler for users who don’t want to be surveilled.

“The feature more surgically targets the problem of cross-site tracking without the breakage and wide-scale ad blocking which occurred with our initial Tracking Protection implementation. It does this by preventing known trackers from setting third-party cookies — the primary method of tracking across sites,” Dolanjski said.

Red panda image via Amit Patel's Flickr photostream, Creative Commons