Third-Party Cookies

For decades, third-party cookies have been the backbone of digital advertising targeting. When you visit a news site, an ad network's cookie follows you to retail sites, social platforms, and email. That cookie reports back: "This person looked at running shoes." Advertisers then use that data to show you running shoe ads everywhere.

Think of it like a private investigator hired by shoe companies who follows you around the mall, takes notes on every store you visit, then reports back to coordinate ads. The cookie is the investigator's notebook.

In marketing tools, third-party cookies power audience segmentation, retargeting campaigns, and cross-site behavioral targeting. When you upload a customer list to Facebook or Google, those platforms match it against cookie data to find lookalike audiences. When you see an ad for something you browsed yesterday on a completely different website, that's third-party cookies at work.

However, Apple's Safari and Mozilla's Firefox have already blocked third-party cookies. Google Chrome—which handles 65% of web traffic—is phasing them out by late 2024. This creates a critical problem: marketers lose visibility into user behavior across the open web, making audience targeting harder and more expensive.

For CMOs evaluating marketing tools today, the practical implication is urgent: any vendor still relying primarily on third-party cookies for targeting will become obsolete. You need solutions built on first-party data (information users willingly give you), contextual targeting (content relevance rather than user tracking), or privacy-safe alternatives like Google's Privacy Sandbox.