Mozilla Explains Why It's Blocking Third-Party Cookies in Firefox 22

Mozilla is making a move to better protect Firefox users from tracking sites by blocking third-party cookies by default. As of Firefox 22, currently in the Nightly channel, only cookies coming from domains visited by the user will be allowed.

Currently, all cookies are accepted by default. Safari is the only major browser that blocks third-party cookies by default, it has done so for over a decade.

The transition will take some time, Mozilla is looking to see how the change will impact websites, but since there is already a major browser that does this, there shouldn't be any major problems.

While the change in policy has to do with tracking cookies, Firefox won't be blocking these cookies outright. If a user visits a domain, for example clicks on an ad, cookies, even tracking cookies, will be accepted.

"Users of this build of Firefox must directly interact with a site or company for a cookie to be installed on their machine. The patch also provides an additional control setting under the 'Privacy' tab in Firefox’s Preferences menu," Mozilla's Alex Fowler, the privacy and public policy chief, wrote.

Mozilla has explained that it is implementing the change because that's what most Firefox users want and it's what it believes is right.

The increasing number of companies that use tracking cookies and the general trend towards better privacy controls were factors in the decision.

"We have a responsibility to advance features and controls that bring users’ expectations in line with how the web functions for them," Fowler explained.

"Mozilla’s users frequently express concerns about web tracking, and we’ve been listening. We are constantly challenging ourselves to deliver a browser that conforms to user expectations while facilitating online innovation," he added.

Firefox 21, which has been pushed to the Aurora channel, also introduced better controls for Do Not Track, making it possible for users to better specify whether they want to be tracked or not.