Blocking Third-Party Hands from the Cookie Jar

Third-party cookies, originating from domains different from the one you're currently visiting, pose a significant privacy concern. For instance, while logging into a website like example.com sets a first-party cookie for authentication, that site might also load images from another domain, such as an advertising network. This seemingly innocuous image request can also set a third-party cookie.

This practice, often involving "tracking pixels," allows advertisers to build detailed profiles of user browsing habits. As Eric Lawrence explains, these cookies, set by unrelated domains, enable trackers to link your visits across multiple websites, creating a comprehensive profile used for targeted advertising or data sales.

The tide is turning, however. Browser developers are increasingly prioritizing user privacy by restricting third-party cookies:

• Brave: Blocks third-party cookies by default.
• Safari: Employs "Intelligent Tracking Prevention," effectively blocking third-party cookies by default (as of February 21, 2019).
• Firefox: Blocks known trackers by default (as of September 3, 2019).
• Edge: Offers adjustable tracking prevention levels; even its "balanced" setting permits essential third-party authentication (as of June 27, 2019).
• Chrome: Planned to block third-party cookies by default (as of February 4th, 2020), initially by defaulting cookies to first-party-only status. Edge and Firefox intend to adopt a similar approach.

While individual browser settings allow for third-party cookie blocking, widespread adoption remains low. As Jeremy points out, the pervasive use of third-party cookies and scripts is responsible for many of the internet's most significant privacy issues. 2019 marked a turning point in the fight for online privacy, with major browsers finally taking decisive action.

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