Understanding Cookies
Cookies are small text files stored on users' browsers that contain information about the user's interaction with websites. Cookies are fundamental to how the web works, enabling features like login persistence, shopping carts, and personalization.
However, not all cookies serve the same purpose. First-party and third-party cookies operate differently, have different security implications, and are used for different purposes.
First-Party Cookies
A first-party cookie is set by the website the user is currently visiting. When you visit example.com, that website can set cookies that are associated with example.com.
First-party cookies are stored in the user's browser and are only sent back to example.com when the user visits example.com. The browser enforces this rule: cookies set by example.com are never sent to other-site.com.
Examples of First-Party Cookies
Session cookies that keep you logged in: When you log in to example.com, the website sets a session cookie containing your authentication token. Every time you visit example.com, this cookie is sent with your request, and the server confirms you're authenticated.
Preference cookies: Websites use first-party cookies to remember your preferences. If you select a light theme or language preference, the website stores this preference in a cookie and applies it on future visits.
Shopping cart cookies: E-commerce websites use first-party cookies to maintain shopping cart contents across sessions.
Analytics cookies: Websites can use first-party cookies to track how you interact with their site (which pages you visit, how long you stay, etc.).
Advantages of First-Party Cookies
User convenience: First-party cookies enable personalization and remember user preferences without requiring login every time.
Site functionality: Many website features (shopping carts, preferences, session management) require first-party cookies to work.
Privacy-friendly: First-party cookies are limited to a single website and cannot track users across different sites.
User control: Users can see and delete first-party cookies associated with specific websites in browser settings.
Privacy Considerations
First-party cookies present fewer privacy risks than third-party cookies because they're limited to a single website. However, they can still track user behavior within that website.
If a website uses first-party cookies to track your activity and then sells that data to advertisers, that data sharing is a privacy concern even though the cookies themselves are first-party.
Third-Party Cookies
A third-party cookie is set by a domain other than the website you're currently visiting. These cookies are typically set by external services embedded in websites, such as advertising networks, analytics providers, or social media widgets.
For example, when you visit example.com and that site contains an advertisement from ads-network.com, the ad-network can set cookies on your browser. These third-party cookies are associated with ads-network.com, not example.com.
How Third-Party Cookies Work
When you visit example.com, which includes an advertisement from ads-network.com:
- Your browser loads the example.com page
- As the page loads, it loads the advertisement from ads-network.com
- ads-network.com sets a cookie in your browser
- Later, when you visit another-website.com (which also includes ads from ads-network.com)
- Your browser sends the ads-network.com cookie along with the request
- ads-network.com can now see that the same user visited both example.com and another-website.com
This allows ads-network.com to track your activity across multiple websites.
Examples of Third-Party Cookies
Advertising cookies: Advertising networks use third-party cookies to track users across websites and build profiles of user interests for targeted advertising.
Analytics cookies from third parties: Some analytics services (like Google Analytics in its traditional third-party form) set cookies that track users across multiple websites.
Social media tracking cookies: Social networks set cookies that track your activity across the web, even on sites where you're not logged in.
Affiliate tracking: Affiliate networks use third-party cookies to track whether users came from an affiliate link and attribute sales accordingly.
Privacy Concerns
Third-party cookies are the primary mechanism for cross-site tracking. A single advertising network can track your browsing across hundreds of websites, building a detailed profile of your interests and behavior.
This tracking happens without explicit user knowledge or consent. When you visit a website, you might not be aware of all the third-party services embedded in it.
The data collected through third-party cookies is often shared, sold, or used for targeted advertising in ways that users don't control.
Key Differences Summarized
| Feature | First-Party | Third-Party |
|---|---|---|
| Set by | The website you're visiting | External services on the website |
| Sent to | Only the setting website | The setting domain across websites |
| Purpose | Site functionality, preferences | Cross-site tracking, advertising |
| Privacy risk | Limited to one site | Can track across many sites |
| User control | Can delete per-website | Harder to identify and manage |
| Regulation | Generally permitted | Being restricted/eliminated |
Browser Handling and Privacy Features
Modern browsers are increasingly restricting or eliminating third-party cookies due to privacy concerns.
Apple's Safari already blocks third-party cookies by default.
Google Chrome is phasing out third-party cookies (though the timeline has extended multiple times).
Firefox blocks third-party cookies from tracking companies by default.
Microsoft Edge allows users to choose blocking levels for third-party cookies.
Many browsers now require user consent before setting cookies (due to regulations like GDPR and CCPA).
Regulatory Context
Several regulations affect cookie use:
GDPR (General Data Protection Regulation) in Europe requires explicit consent for non-essential cookies (including most analytics and advertising cookies).
CCPA (California Consumer Privacy Act) gives California residents the right to know what data is collected and to opt out of data sales.
PIPEDA in Canada and similar regulations in other jurisdictions all require transparency and consent for tracking.
ePrivacy Directive in Europe specifically regulates cookies and requires consent for non-essential cookies.
Due to these regulations, most websites show cookie consent banners asking users to accept tracking cookies.
First-Party Cookies and Privacy Concerns
While first-party cookies are more privacy-friendly than third-party cookies, they're not risk-free.
Websites can use first-party cookies to build detailed profiles of user behavior.
When websites share data with third parties, first-party cookies can contribute to cross-site tracking if the same data is shared across multiple sites.
Some websites use server-side tracking (tracking users in logs and databases rather than cookies) instead of or in addition to cookies. Server-side tracking is harder for users to control.
Technical Considerations
Cookie Attributes
Cookies can have various attributes that affect their behavior:
SameSite attribute: Controls whether cookies are sent with cross-site requests. Can be Strict (never sent with cross-site requests), Lax (sent with top-level navigations), or None (always sent).
Domain attribute: Specifies which domains can access the cookie.
Path attribute: Specifies which paths on a domain can access the cookie.
Secure attribute: Requires cookies only be sent over HTTPS.
HttpOnly attribute: Prevents JavaScript from accessing the cookie (only server can access it).
The SameSite attribute is particularly important for controlling third-party cookie behavior and is being used to reduce cross-site tracking risks.
Alternatives to Third-Party Cookies
As third-party cookies are phased out, alternatives are emerging:
First-party data collection: Websites can collect data directly from users through logins and explicit tracking opt-ins.
Server-side tracking: Websites can track users on their own servers without relying on cookies.
Contextual advertising: Showing ads based on page content rather than user history.
Privacy-preserving technologies: Technologies like Federated Learning of Cohorts (though this is controversial) and Privacy Sandbox APIs (proposed by Google) aim to enable advertising without individual tracking.
User Privacy and Cookie Management
Users can manage cookies in browser settings:
- View and delete cookies from specific websites
- Block all cookies or third-party cookies
- Clear cookies on browser close
- Use private/incognito mode to prevent persistent tracking
However, many users don't know how to manage cookies or don't realize which sites are tracking them.
Implications for Website Owners
If you operate a website:
- Use first-party cookies for legitimate site functionality (sessions, preferences)
- Obtain clear consent for analytics and advertising cookies
- Respect user cookie preferences and provide easy options to opt-out
- Be transparent about what cookies you use and why
- Review third-party services on your site and understand what cookies they set
- Consider privacy-preserving alternatives to third-party tracking
If you use advertising networks or analytics services, understand what cookies they set and ensure you're complying with regulations.
The distinction between first-party and third-party cookies is fundamental to understanding web privacy and tracking. First-party cookies enable site functionality and personalization with limited privacy concerns, while third-party cookies are primarily used for cross-site tracking and targeted advertising. Understanding this distinction helps you make informed decisions about cookie use and manage your privacy effectively.
