Home Data Mozilla Delays Blocking Third-Party Cookies

Mozilla Delays Blocking Third-Party Cookies

SHARE:

firefoxMozilla has postponed activating the third-party blocking feature on its latest browser, Firefox 22, according to an update on its developer page.  The blocking feature has been postponed “to collect data on the effect of blocking some third-party cookies,” according to the blog post.

A Mozilla spokesperson provided the following statement: “Mozilla has been actively gathering input from users and stakeholders across the digital media ecosystem on the potential impact of the third-party cookie patch. We are ensuring proper measurement of its actual effects and will hold it in the Aurora testing build for at least one more six-week release cycle to allow for that.”

Sid Stamm, lead privacy engineer at Mozilla, shed more light on the topic, noting in a discussion forum that measuring the impact of blocking third-party cookies on Firefox’s browser, is “not as simple as we originally thought” since there is “some data structure to do and potentially [performance] concerns too.”

Jonathan Mayer, the privacy advocate and graduate student at Stanford University who designed the Firefox cookie-blocking feature, agreed, noting that Mozilla would need another release cycle to catch up on the measurements. “In particular, I’d like to improve our understanding of false positives (i.e. trusted third parties) and false negatives (e.g. untrusted first parties that are grandfathered in or that the user is temporarily redirected through),” Mayer wrote.

The Mozilla Foundation, makers of the Firefox Web browser, made headlines earlier this year when it revealed plans to block third-party advertising cookies by default on Firefox 22. Apple’s Safari browser already blocks third-party cookies. Advertising trade groups like the Association of National Advertisers have blasted Mozilla’s cookie-blocking feature, describing it as “a dangerous and highly disturbing development.”

Must Read

For Super Bowl First-Timers Manscaped And Ro, Performance Means Changing Perception

For Manscaped and Ro, the Big Game is about more than just flash and exposure. It’s about shifting how audiences perceive their brands.

Alphabet Can Outgrow Everything Else, But Can It Outgrow Ads?

Describing Google’s revenue growth has become a problem, it so vastly outpaces the human capacity to understand large numbers and percentage growth rates. The company earned more than $113 billion in Q4 2025, and more than $400 billion in the past year.

BBC Studios Benchmarks Its Podcasts To See How They Really Stack Up

Triton Digital’s new tool lets publishers see how their audience size compares to other podcasts at the show and episode level.

Privacy! Commerce! Connected TV! Read all about it. Subscribe to AdExchanger Newsletters
Comic: Traffic Jam

People Inc. Says Who Needs Google?

People Inc. is offsetting a 50% decline in Google search traffic through off-platform growth and its highest digital revenue gains in five quarters.

The MRC Wants Ad Tech To Get Honest About How Auctions Really Work

The MRC’s auction transparency standards aren’t intended to force every programmatic platform to use the same auction playbook – but platforms do have to adopt some controversial OpenRTB specs to get certified.

A TV remote framed by dollar bills and loose change

Resellers Crackdowns Are A Good Thing, Right? Well, Maybe Not For Indie CTV Publishers

SSPs have mostly either applauded or downplayed the recent crackdown on CTV resellers, but smaller publishers see it as another revenue squeeze.