A third-party cookie is a cookie that's placed on a user's device -- computer, cellphone or tablet -- by a website from a domain other than the one the user is visiting.
Understanding Third-Party Cookies
Third-party cookies are a type of tracking technology used in web browsers. Unlike first-party cookies, which are set by the website you are directly visiting to remember things like login status or shopping cart items, third-party cookies are placed by a domain different from the one shown in your browser's address bar.
These cookies are also commonly known as trackers or cross-site cookies because they are designed to follow users across multiple websites.
How Third-Party Cookies Work
When you visit a website, it might include content from a different domain. This could be an embedded video player, a social media sharing button, or most commonly, an advertisement served by an ad network.
If this external content or ad server wants to set a cookie on your browser, that cookie will be associated with the domain of the external server, not the website you are currently viewing. Since the cookie's domain is different from the site you are actively visiting, it is classified as a third-party cookie.
Because the same third-party domain (like an ad network) can appear on many different websites, it can use its cookie to identify your browser and track your activity as you move from one site to another.
Primary Uses and Examples
Third-party cookies are most frequently used for online advertising. Their main purpose is to enable tracking for various advertising and marketing activities, such as:
- Targeted Advertising: Building a profile of your interests based on the websites you visit to show you more relevant ads.
- Retargeting: Showing you ads for products or services you previously viewed on a different website.
- Ad Measurement: Tracking which ads you've seen and clicked on to measure campaign effectiveness.
- Cross-Site Tracking: Understanding user behavior across a network of websites to inform marketing strategies.
Example: Imagine you visit Website A (a news site) and it displays an ad from Ad Network X. Ad Network X places a third-party cookie on your browser. Later, you visit Website B (a blog), which also uses Ad Network X. Ad Network X can read the cookie it placed earlier and know that the same user who visited Website A is now on Website B. Over time, by appearing on many sites, Ad Network X can build a detailed picture of your browsing habits across the web.
Third-Party vs. First-Party Cookies
Understanding the distinction is key:
| Feature | First-Party Cookies | Third-Party Cookies |
|---|---|---|
| Set by | The website domain the user is currently visiting | A domain different from the website the user is visiting |
| Purpose | Site functionality (login, cart, preferences) | Tracking across sites (advertising, analytics) |
| Accessibility | Only accessible by the domain that set it | Can be accessed by the third-party domain on any site where its content/ads are loaded |
| User Concern | Generally considered less intrusive | Often associated with privacy concerns due to cross-site tracking |
Privacy Concerns and Management
Due to their ability to track users across disparate websites, third-party cookies have raised significant privacy concerns. They enable companies to build detailed profiles of individuals' online activities without direct consent in many cases.
Many web browsers and regulatory frameworks (like GDPR and CCPA) have implemented measures to limit or block third-party cookies by default, giving users more control over their online privacy.
Users can typically manage third-party cookies through their browser settings:
- Blocking all third-party cookies: Prevents any third-party domains from setting or reading cookies.
- Blocking third-party cookies in Incognito/Private browsing mode: Limits tracking during private sessions.
- Clearing existing cookies: Removes cookies stored on your device.
While blocking third-party cookies can enhance privacy, it might occasionally affect the functionality of some websites that rely on them for certain features, although this is less common compared to blocking first-party cookies.
