• by Wendy Davis , Staff Writer @wendyndavis, November 3, 2015

Mozilla's newest version of Firefox, released today, enables users to block third-party ads and prevent data collection by ad networks, analytics companies and social widgets such as Facebook's "like" button.

Firefox's new Private Browsing with Tracking Protection setting "actively blocks content like ads, analytics trackers and social share buttons that may record your behavior without your knowledge across sites," Nick Nguyen, vice president of Firefox Product, wrote today in a blog post. 

The tracking protection feature will only be available when people select Firefox's "private browsing" mode to navigate the Web.

Mozilla boasts that its new tool offers better anti-tracking features than those of the other major browser developers. "With the release of Tracking Protection in Firefox Private Browsing we are leading the industry by giving you control over the data that third parties receive from you online," Nguyen writes.

In the past, Firefox's private browsing feature deleted users' cookies and their browser histories when they closed private windows. But the new "tracking protection" feature goes further by preventing cookies, pixels, and other tracking mechanisms from ever loading.

The tool also allows users to go back and forth between private and non-private browsing, "depending on how much data they want to share at any given time," Nguyen says in an email to MediaPost.

News of Mozilla's move was cheered by the Electronic Frontier Foundation's chief computer scientist Peter Eckersley. "This is the kind of measure that's necessary to offer a genuine private browsing experience," Eckersely tells MediaPost.

At the same time, the move doesn't appear to be as aggressive a stance against third-party trackers as the company planned in 2013. That February, Mozilla said Firefox would soon start blocking third-party tracking cookies by default.

That announcement drew heated complaints from industry groups like the Association of National Advertisers, which called the decision "extraordinarily counterproductive for consumers and business.” IAB general counsel Mike Zaneis called it a "nuclear first strike" against the ad industry.

In May of that year, Mozilla retreated. The company said at the time that the cookie-blocking patch needed more work.