Mozilla's Firefox browser will soon block some third-party cookies by default, privacy advocate Jonathan Mayer announced on Friday.
The upcoming Firefox 22, set for release in June, will
include a patch that blocks some third-party cookies -- like those set by ad networks. Firefox's default settings will still allow first-party cookies, as well as cookies from third parties that
users have a relationship with. "Only websites that you actually visit can use cookies to track you across the web," Mayer writes in a blog post explaining the patch, which he developed.
Those settings are similar to the defaults in Safari, although Mayer characterized
the Firefox cookie defaults as a "slightly relaxed version" of Safari's settings. Firefox currently commands around 20% of the desktop browser market -- four times as much as Safari.
Online ad
companies will almost certainly try to rally opposition to the move. Mike Zaneis, general counsel at the Interactive Advertising Bureau, tweeted on Saturday that the setting "would be a nuclear first strike" against the ad
industry.
The move comes around 18 months after the World Wide Web Consortium -- a group of computer scientists, industry representatives and privacy advocates (including Mayer) -- began
trying to develop standards for responding to do-not-track headers. Those headers, now offered by all the major browsers, are aimed at letting people permanently opt out of online behavioral
advertising. But the headers don't actually prevent tracking. Instead, they send signals to publishers and ad networks, which those companies decide how to interpret.
So far, the W3C hasn't
been able to agree on how to interpret the signals. Some privacy advocates previously warned that if W3C fails to reach a consensus, browser manufacturers might follow Safari's lead and simply block
third-party cookies.