ReTargeter Blog

Firefox and the Third-Party Cookie: What Mozilla’s Privacy Move Means for Marketers

Firefox and the Third Party Cookie

Mozilla, the maker of Firefox, has recently announced they will be blocking third-party cookies by default in an upcoming version of the browser. The update is scheduled to ship to the public this summer. The announcement (which you can read in full here) comes less than a year after Microsoft made a big stir in the online world by announcing it would be shipping Internet Explorer 10 with Do Not Track enabled by default.

At the time of Microsoft’s announcement, Mozilla’s privacy and public policy head, Alex Fowler, wrote on Mozilla?s blog:

If DNT is on by default, it’s not a conversation. For DNT to be effective, it must actually represent the user’s voice.

You may now be thinking, what’s the difference between what Microsoft did and what Mozilla is doing? What are the implications for marketers and do they differ from the potential ramifications DNT by default?

Technically, there is a distinction, but the end goal is roughly the same, and the ramifications are also similar. But first, let’s dive further into what Mozilla’s announcement actually said:

Using and Blocking Third-Party Cookies

For those who need a refresher, a third-party cookie is any cookie that isn’t from the website you’re actually visiting (even if the website you visit has entered into their code). You can read this cookies guide if you need a little more help. Here’s an example: let’s say I log into Amazon, and Amazon stores my username and password, they’re using a first-party cookie because they’re storing information that I gave them on their own website. But if Amazon utilizes retargeting via a third party (let’s say it’s ReTargeter), and they have a ReTargeter pixel up on their site, the pixel will be blocked and a cookie will not be dropped because ReTargeter is a third party whose site I haven’t yet visited. However, if I were to visit ReTargeter, then return to Amazon, Firefox would not block a ReTargeter cookie.

Right now, Safari is the only major browser to block third-party cookies by default, but under Safari’s default settings, the ReTargeter cookie would always be blocked. While Mozilla’s Alex Fowler did credit Safari with inspiring the new feature, Firefox does seem to be less draconian in its approach.

The above example was focused on advertising, but third-party cookies are also used for analytics programs, sharing widgets, and to carry out other important web functions.

How Is This Different from Do Not Track?

When Microsoft announced its intention to ship a new version of Internet Explorer with Do Not Track enabled by default, there was almost instant backlash?including from Mozilla. But what?s the difference?

Do Not Track does not actually block third-party cookies . It’s a browser setting that signals to other websites and ad networks not to track any third-party cookie dropped on a browser where a user has turned DNT on. It was actually Firefox who first developed DNT back in 2011, but before Microsoft’s announcement no one had ever suggested using DNT as a default setting. For a more comprehensive look at DNT and its history, check out our overview: A Marketer?s Guide to Do Not Track.

Unlike the DNT setting, disabling third-party cookies by default doesn’t send a signal, it simply doesn’t allow cookies to drop. Functionally, it’s rather similar to DNT, except it cannot be easily ignored, while DNT requires the buy-in from ad networks and other third parties.

What Does It Mean for Marketers?

By and large, the advertising industry has not responded positively to Firefox’s news. Mike Zaneis, General Counsel for the IAB, has been quoted extensively for his observation that Firefox’s new policy is a “nuclear first strike against [the] ad industry.”

Others in the advertising industry responded similarly, though with less rhetorical force.  Here’s what Joshua Koran, SVP of product management at Turn, had to say:

Mozilla is making a decision by default, without giving consumers a choice. We are strong advocates of the rights and preferences of consumers and anticipate that as with similar unpopular and anti-competitive actions, this unilateral initiative will be rolled back or will have minimal impact on the online advertising industry.

And it’s not only the advertising industry that’s reacting. Ramsey McGrory, CEO of social sharing platform AddThis, also weighed in:

“While the intentions of FireFox are most likely good, the unintended consequences may outweigh the benefit that’s achieved. It just reinforces that the waters are choppy when it comes to anything having to do with data and privacy.

Though many marketers associate this type of policy change with advertising, it’s just as likely to affect sharing widgets like AddThis, third-party analytics programs, and more. Ultimately, small publishers who rely third-party cookies for ad revenue are likely to be hardest-hit by this change.

The web as we know it can’t function without first and third-party cookies; companies rely on first-party cookies to track information throughout the purchase cycle and improve the web experience for the user, and many companies and publishers rely on third-party cookies to track site performance, monetize content, and more.

It’s also important to note that this change is still not imminent, and it’s certainly possible if not likely that changes will be made or the patch will be abandoned prior to launch.


Ultimately, the effects on behavioral advertising are not going to be catastrophic. The industry is still looking for the right balance in serving our clients? goals and satisfying the needs of consumers, who ultimately deserve more transparency and openness. Industry organizations like the IAB, DAA, and Council for Accountable Advertising need to continue to work together to underscore the value of relevant ads and explain that the risks to privacy are smaller than many consumers think.



Case Study – Watters

Watters Logo | ReTargeter

Watters is the brainchild of designer Vatana Watters. For over 30 years, it has been the leader in offering luxurious designer bridal gowns, innovative bridesmaids dresses, classic special occasion dresses for mothers of the wedding, and adorable dresses for flower girls and junior bridesmaids around the world. Selling primarily at trunk shows and in third-party […]

Read more