14 DAY TRIAL // Mozilla is backing down on its decision to block third-party cookies by default in Firefox. Initially, the feature was supposed to be part of Firefox 22. But now that it's in the beta channel, third-party cookie blocking has been disabled by default.
Apple has been doing this for years with Safari, and Mozilla wanted to start blocking third-party cookies which are mainly used for tracking and targeted ads, with or without the users even realizing it.
Mozilla has evaluated the impact of the feature while Firefox 22 was in Aurora and determined that there are some problems with the approach, problems that need to be addressed before going forward.
"We have heard important feedback from concerned site owners. We are always committed to user privacy, and remain committed to shipping a version of the patch that is 'on' by default," Mozilla's Brendan Eich explained.
"We are mindful that this is an important change; we always knew it would take a little longer than most patches as we put it through its paces," he added.
In the testing so far, Mozilla has encountered two big types of problems. On the one hand, there are false positives, when Firefox blocks cookies that are actually for the same site but come from a different domain.
This is common with sites that store static resources on CDNs for example, as most major sites do. Blocking cookies that don't come from the same domain can break some sites.
At the same time, just because a user visited a site at one point is not reason enough to trust it. Users may accidentally click on an ad, or a site they previously trusted may start using tracking cookies.
Mozilla wants to fix these issues before enabling the feature by default for everyone. For now, third-party cookie blocking will stay off by default in Firefox beta and stable, but will be enabled in Aurora to facilitate testing of improvements.