ThirdPartyCookies

Third-party cookies are HTTP cookies created by a domain other than the one a user is visiting. They typically arise when a page loads resources from third parties, such as advertisers, analytics services, or social media widgets. When the third party sets a cookie in the user’s browser, that cookie can be sent back to the third-party domain on subsequent requests to any site that loads those resources, enabling cross-site tracking.

Their main uses include advertising targeting and frequency controls, analytics, and social features. They can help deliver relevant content or measure ad effectiveness, but they also enable persisting profiles of users’ browsing across sites without explicit interaction.

Privacy concerns and regulatory considerations have led to changes in policy and technology. Laws such as the GDPR and CCPA govern consent and data handling for cookies, while many browsers have introduced restrictions on third-party cookies. Technical measures include the SameSite attribute, which limits when cookies are sent with cross-site requests, and browser-wide blocking or isolation of third-party data. As a result, third-party cookies are increasingly blocked by default or rendered of limited utility in many contexts.

In response, the industry has pursued alternatives and reforms, including consent management, first-party data strategies, and privacy-preserving approaches under initiatives like Privacy Sandbox. Adoption varies by region and publisher, with a general trend toward reducing reliance on third-party cookies for tracking and targeting.