Third-party cookies have powered digital advertising for over two decades. They help marketers understand user behavior, measure ad performance, and personalize campaigns. But with stricter privacy laws and evolving browser technology, the future of third-party cookies is uncertain.
In this 2025 guide, you’ll learn what third-party cookies are, how they work, why they matter, and what businesses should do to prepare for a privacy-first future.
What Are Third-Party Cookies
Cookies are small text files stored in your browser whenever you visit a website. They help websites remember your preferences, sessions, and actions.
Cookies that originate from the site you’re visiting are called first-party cookies. When another company, such as an advertising or analytics provider, places cookies through that site, they’re called third-party cookies.
Because they come from external domains, third-party cookies can track user activity across multiple websites. This tracking allows advertisers to deliver relevant ads, measure conversions, and build audience profiles.
Example: You visit a fashion store online, and a Meta or Google Ads tag drops a cookie into your browser. Later, when you read the news or scroll through another website, you start seeing ads for the same sneakers. That’s how third-party cookies work.
How Do Third-Party Cookies Work
The process behind third-party cookies follows a series of simple steps:
- A webpage loads third-party content. This can include ads, analytics tools, or embedded social media widgets.
- Your browser requests data from the third-party server. The request allows the external domain to interact with your browser.
- A cookie is created. The third-party server stores a unique identifier that can recognize your browser later.
- Tracking continues across sites. When you visit another site using the same third-party service, the cookie identifies you again.
- Data is analyzed and used. Marketers use the data for retargeting, personalization, and campaign measurement.
In short, third-party cookies are what make cross-site tracking and ad targeting possible.
Why Are Third-Party Cookies Important for Marketers
Third-party cookies have long been essential for digital marketing because they allow businesses to:
- Understand audience behavior across multiple websites and sessions.
- Retarget interested users who visited but didn’t convert.
- Measure ad performance and link conversions to campaigns with GA4 tracking to ensure every conversion is captured accurately.
- Optimize ad spend based on accurate attribution data.
Without them, digital advertising becomes less personalized and less measurable. However, this same level of tracking has also raised serious privacy concerns.
Why Are Third-Party Cookies Being Phased Out
Third-party cookies collect vast amounts of user data, often without explicit consent. This has created growing concerns around privacy and compliance.
Here’s why major browsers and regulators are taking action:
- Browser restrictions: Safari and Firefox already block third-party cookies by default, and Chrome is gradually implementing similar protections.
- Data privacy regulations: Laws such as GDPR (Europe) and CCPA (California) require businesses to obtain clear consent before collecting user data. Google’s Consent Mode v2 helps balance compliance and conversion tracking.
- User demand for transparency: More people are using privacy tools, ad blockers, and cookie managers to control what information they share.
As a result, third-party cookies are becoming less reliable, forcing businesses to explore new ways to measure performance and reach their audiences responsibly.
Google Chrome’s 2025 Update: The Privacy Sandbox Explained
In 2025, Google revised its original plan to completely remove third-party cookies from Chrome. Instead, Chrome now gives users the power to decide whether to allow or block them through its Privacy and Security settings.
To maintain ad functionality, Google introduced the Privacy Sandbox, a collection of APIs that allow privacy-safe tracking and measurement without exposing personal data.
Key features include:
- Protected Audience API: Enables interest-based ad targeting without individual tracking.
- Attribution Reporting API: Helps measure ad conversions while protecting user anonymity.
- IP Protection: Hides users’ IP addresses to prevent cross-site fingerprinting.
This approach balances user privacy with business needs. Rather than ending third-party cookies instantly, Google is transitioning toward privacy-safe tracking methods that respect user consent. Brands adopting GTM server-side setups are already seeing stronger data accuracy under Chrome’s Privacy Sandbox.
How to Check or Manage Third-Party Cookies
You can easily check whether a website uses third-party cookies:
- Using Chrome DevTools: Right-click, select Inspect, go to the Application tab, and view the Cookies section. Domains different from the site’s main URL represent third-party sources.
- Browser extensions: Tools such as Ghostery, Cookiebot, or uBlock Origin show active cookies and trackers.
- Online scanners: Sites like CookieServe scan and list all cookies used on a webpage.
To block third-party cookies:
- Chrome: Go to Settings → Privacy and Security → Cookies and other site data → Block third-party cookies.
- Firefox: Settings → Privacy and Security → choose “Strict.”
- Safari: Preferences → Privacy → select “Prevent cross-site tracking.”
- Edge: Settings → Privacy, search, and services → set Tracking prevention to “Strict.”
Blocking cookies improves privacy but may reduce the functionality of certain ads, analytics, or social plugins.
Best Alternatives to Third-Party Cookies in 2025
As the industry moves toward privacy-first solutions, marketers are exploring several effective alternatives:
- First-party data: Collect information directly from your website visitors using consented analytics and CRM tools.
- Zero-party data: Gather data that users voluntarily share through surveys, forms, or preference centers.
- Contextual targeting: Serve ads based on the content of the page rather than individual behavior.
- Server-side tracking: Move event tracking to your own server for greater accuracy and compliance.
- Hybrid models: Combine first-party data with contextual insights for a more complete view of performance.
These approaches not only improve data accuracy but also build trust with users by being transparent about data usage.
What Should Businesses Do Right Now?
- Audit your website. Identify which third-party cookies are active and why they’re needed, then follow this tracking fix guide to repair broken analytics before adopting new methods.
- Invest in first-party data. Build customer relationships that encourage users to share information directly.
- Adopt server-side tracking. Tools like Conversios simplify the process while maintaining compliance.
- Update consent banners and policies. Clearly communicate how cookies are used and give users easy control options.
- Follow industry updates. Keep track of Google’s Privacy Sandbox announcements and evolving privacy regulations.
The Future of Advertising Beyond Third-Party Cookies
Third-party cookies will continue to exist in the short term, but their importance is fading. The future of digital marketing lies in transparency, consent, and data accuracy.
Marketers who prioritize ethical data collection and privacy-first analytics will not only stay compliant but also earn stronger customer trust.
In the long run, building meaningful connections based on permissioned data will drive better results than any cookie-based system ever could.
Frequently Asked Questions
Q: Are third-party cookies illegal?
No. They are not illegal, but businesses must use them responsibly and comply with privacy regulations such as GDPR and CCPA.
Q: How can I check which cookies a website uses?
You can use browser developer tools or cookie-checking extensions to identify cookies set by external domains.
Q: What is the best alternative to third-party cookies?
The most effective replacements are first-party data collection, contextual targeting, and server-side tracking.