Mozilla on Tuesday announced that the latest version of its Firefox browser will let users opt to block online trackers, such as cookies and other tools that advertisers and others use to follow Internet users from site to site.

Firefox, like all major browsers, already has a "private browsing" mode, for those who want to keep the program from recording their history or other habits. Tracking protection is designed to build upon that feature, the company said. The idea, according to Mozilla vice president of product Nick Nguyen, isn't to make an ad blocker - but rather to set clear guidelines that may, in time, improve the quality of ads users see.

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"The goal is not to block ads, but to block tracking," he said in an interview with The Washington Post, noting that not all advertising is stripped out of pages when the feature is turned on.


Debate about the state of the online ad business came to the fore in September after Apple added support for ad blocking apps in its latest mobile operating system, iOS 9. Apple's move stoked lots of conversation about the relationship between online advertisements, which most people hate, and free, ad-supported content, which most people love.

Mozilla's approach shows there may be room in the debate for compromise, that strikes a balance between user privacy and advertising. In time, Nguyen said, he hopes that advertisers and publishers will learn to adapt their advertising to the tracking block standards and design products that serve the needs of both consumers and companies.

"It's not that we're trying to build something that blocks all advertising, he said. "If people could get everything for free that's the choice they would make. But we don't want that." What Mozilla does want, he said, is for the Internet to continue to grow.

Recent stirrings from the advertising industry indicate that companies are clearly hearing consumer frustrations with ads. In a recent blog post, the Interactive Advertising Bureau admitted that the industry had "messed up" the Web by overloading it with large, occasionally invasive ads. In response, the IAB announced a new LEAN ads program - for Light, Encrypted, Ad-choice supported and Non-invasive.

Look back to pop-up blocking, that didn't kill all advertising.

Nguyen is confident that the Firefox tracking blocker - with its clear guidelines about what's allowed and what's not - can speed along a change for the better.

"Look back to pop-up blocking," he said. "That didn't kill all advertising, just that which users didn't want to see."

The new version of Firefox, with the tracking blocker, is available for download starting Tuesday. Users will have the option to turn it on or off, as they do with private browsing. Nguyen said that the non-profit expects that the audiences for both services would be similar.

But when asked how many of the browser's users that might be, he said that Firefox doesn't actually track how many people use its privacy-focused features.