What are third-party cookies and how do they work?

Third-party cookies are used by an external domain or server that the users are not currently visiting. Websites use such cookies to keep track of the users' browsing habits so that other online platforms or mobile applications can show them personalized advertisements related to their interests.

For instance, if someone searches for laptops to buy, their browsing activity may be tracked and saved using third-party cookies by the site.

As a result, they may encounter laptop advertisements when they visit other websites. Third-party cookies will allow advertisers to deliver targeted ads based on the saved user's interests and preferences.

Working mechanism

Here is the step-by-step breakdown of how third-party cookies work:

Set up a cookie: A website using a third-party cookie can store the cookie file on the user's side. A cookie file mainly contains a name-value pair along with some other attributes. The third-party websites use the name-value pair to identify what data to retrieve and where to send data. You can access the cookie file by following the steps mentioned below:

Track browsing data: The cookie file then keeps a record of users' browsing activities to determine their tastes or tendency.
Build a profile: The cookie creates a user profile based on the accumulated data of the user. This profile contains details about the user's interests, preferences, and behaviors. It also keeps on updating depending upon how the user browses with time.
Data sharing: Some websites have certain portions on their web pages dedicated to external sites to host their domains. These external sites use the profiles built by third-party cookies to show the related content in their dedicated portions.

The slides above explain how website A sets the cookie to the user's system as soon as the user visits it. When the same user visits website B, it retrieves relevant information from the previously stored cookies created by website A, allowing website B to display related content.

Conclusion

Although third-party cookies may not pose a significant threat to the users, they raise some privacy concerns. The users may feel uneasy about their browsing behavior getting tracked by the websites they have not directly engaged with. The primary purpose of third-party cookies is to improve the user experience by showing them the content they are interested in.