Although Mozilla has not publicized the change, developers and company executives, including Brendan Eich, Mozilla's CTO, and Asa Dotzler, the Firefox desktop product manager, debated the new policy on a discussion thread for several weeks before approving the change.
"I'm in favor of moving forward on this, cautiously," Dotzler said Feb. 11 on the thread. "As long as we have confidence at each step of the way that we're not breaking significant numbers of users or sites, this is a good move."
Mozilla will be following in the footsteps of Apple's Safari, which also blocks third-party cookies by default. "The new Firefox policy is a slightly relaxed version of the Safari policy," said Mayer in an FAQ published on his personal blog.
Even so, at least one online ad official slammed Mozilla for making the change. "Firefox to block 3rd party cookies? This default setting would be a nuclear first strike against ad industry," said Mike Zaneis, general counsel for the Interactive Advertising Bureau (IAB), on Twitter Saturday. The IAB is one of several advertising organizations that has been fighting other privacy moves by browser makers, including Microsoft's decision to set "Do Not Track" on by default in Internet Explorer 10 (IE10).
"Second strike, technically (Safari)," retorted Justin Brookman, director of consumer privacy at the Center for Democracy and Technology, also on Twitter.
All browsers, including Firefox, have settings that let users manually switch off all cookies, or refuse those from third-party sites. But only Safari currently blocks all third-party cookies by default. Safari's small share -- in January, Net Applications pegged it as just 5.2% -- was likely too low to trigger the online ad industry's concern. Firefox is a different beast: According to Net Applications, Firefox was the second-most-used browser last month, with a 19.9% share globally.
But Mozilla didn't view the change as a first strike of any kind, nuclear or otherwise, aimed at online advertising. "We are not trying to stop tracking with this feature," Mozilla's Dotzler said on the discussion thread Sunday. "We are trying to make tracking relationships more obvious to the user."
It would not in Mozilla's self-interest to disrupt the online ad industry, as it generates the bulk of its revenue from a deal with Google, which pays the browser maker a reported $300 million a year for setting Google's search engine as Firefox's default.