Third party cookies are small pieces of data stored on a user’s device by a domain that is different from the site the user is actually visiting. They were created to help advertisers, analytics platforms, and other external services understand user behavior across multiple websites, enabling targeted ads, cross site tracking, and personalized experiences.
Today, third party cookies are being phased out by nearly all major browsers, which has reshaped how companies measure performance, attribute conversions, and reach audiences online.
When you visit a website, that site can store information on your device. These are first party cookies, and they help with basic functions like remembering your login or keeping items in your shopping cart.
Third party cookies come from a completely different domain. They load through scripts, pixels, or tags that the website uses from external partners. For example, an ad network, a retargeting platform, or a measurement tool may place its own cookie when a user visits a site that uses its services.
These cookies allow external companies to track user activity across many sites, not just one. This is what made retargeting and cross site attribution possible for years.
Here is a simple way to understand the process:
This creates a cross site view of the user, which allows advertisers to:
For more than a decade, these cookies powered the digital advertising ecosystem. They made it possible to:
Track people across multiple websites
Advertisers could understand user journeys, even when they moved across entirely different sites.
Build detailed audience segments
Interests, browsing patterns, shopping intent, and more could be inferred from cross site activity.
Measure ad performance
They helped identify which ads led to conversions, creating the foundation for modern performance marketing.
Enable retargeting
If a user visited a product page but did not buy, third party cookies made it possible to show them relevant ads elsewhere.
Concerns around privacy and data protection have led browsers to reduce or eliminate support for third party cookies.
Safari, Firefox, Brave, and others already block them by default. Google Chrome, which holds the largest market share, is also moving toward deprecation.
The main reasons include:
This shift is pushing advertisers and brands to adopt privacy safe alternatives based on first party data and server side tracking.
The end of third party cookies does not mean the end of targeting or measurement. Instead, it pushes the industry toward safer, more transparent methods.
Common alternatives include:
First party data
Information collected directly from a user with consent. This is becoming the core of modern marketing.
Server to server tracking
A direct connection between advertiser servers and measurement partners for secure, reliable attribution.
Privacy sandbox technologies
Google’s proposals to support interest based advertising without exposing individual user data.
Identity solutions
Various tools that allow consent based identification such as hashed emails.
Contextual advertising
Targeting based on the meaning of the page rather than user history.
Most tracking cookies are third party cookies, but not all of them. Some tracking can be done with first party cookies too.
Yes. They track users across multiple sites, which is why they have become the focus of privacy regulations.
Yes, but they must rely on first party data, app based identifiers, or privacy safe solutions such as server side tracking.
Most do. Chrome is in the process of removing them but still supports them in limited scenarios.
Every major browser offers built in settings to block them.