Retargeting, Remarketing, Pixels, Cookies and Google Analytics 4: Tracking in the Privacy-First Era

As online privacy becomes increasingly important, understanding how cookies work—and how tools like Google Analytics 4 (GA4) and the Facebook Pixel track user activity—has never been more vital.

Here’s an overview of the differences between first-party and third-party cookies (with examples), the evolution from Google Universal Analytics (UA) to GA4, and how remarketing (or retargeting, in Facebook’s terminology) adapts in this new environment.

This article is relevant to advertisers who build audiences, use remarketing or retargeting, or anyone who wants to understand cookies and tracking in 2025.

1. Understanding Cookies: First-Party vs. Third-Party

First-Party Cookies

  • Definition: Cookies created and stored by the domain (website) you’re currently visiting.
  • Common Uses & Examples:
    • User Preferences: A shopping site storing your language or currency preference in a cookie named site_lang under its own domain (e.g., example.com).
    • Login Status: A membership website placing a secure cookie named session_id so you remain logged in as you move across pages.
    • Shopping Cart: An e-commerce platform maintaining your cart items via a cookie cart_info under example.com.
  • Privacy Implications:
    • Generally considered less invasive, as they only track user activity on the site that sets them.
    • Do not typically allow cross-site tracking unless combined with other technologies.

 

Third-Party Cookies

  • Definition: Cookies placed on a user’s device by a domain other than the one they’re currently visiting.
  • Primary Purpose & Examples:
    • Advertising: An ad network like DoubleClick (now Google Marketing Platform) might set a cookie named _gads from doubleclick.net while you’re on example.com.
    • Cross-Site Tracking: A social media plugin could store cookies from its own domain (e.g., facebook.com) to track user actions across multiple sites.
  • Privacy Concerns:
    • Invasive Tracking: These cookies can follow users across many websites, building detailed profiles.
    • Browser Restrictions: Many browsers (Safari, Firefox, and increasingly Chrome) are blocking or phasing out third-party cookies, reflecting a push for more privacy.

2. The Evolution of Google Analytics

Universal Analytics (UA)

  • How It Worked
    • Relied heavily on third-party cookies to track user activity across sessions and even multiple sites.
    • Provided granular user-level data and robust remarketing options.
  • Privacy Challenges
    • Cross-site tracking raised concerns under stricter privacy laws (e.g. GDPR, CCPA).
    • Reliance on Third-Party Cookies: As browsers started blocking these cookies, UA’s model became increasingly unsustainable.
  • Reason for GA4
    • One major factor behind Google’s transition to GA4 was to address these privacy challenges and reduce reliance on third-party cookies.

 

Google Analytics 4 (GA4): A Privacy-Focused Approach

  • Why GA4?
    • Designed to function within modern privacy regulations and browser restrictions.
    • Uses an event-based data model and machine learning, rather than relying primarily on third-party cookies.

 

Key Tracking Methods in GA4

  1. First-Party Cookie Creation  
    • GA4 sets cookies under your own site’s domain, creating a unique client ID.
    • Data is specific to your site, aligning with privacy regulations and modern browser policies.
  2. Alternative Tracking Techniques  
    • Event-Based Tracking: Focuses on user actions (page views, button clicks, scrolls, etc.).
    • Machine Learning: Fills gaps where cookies or user IDs aren’t fully available.
    • Probabilistic Cross-Device Matching: Uses statistical modeling to identify users across devices without explicit third-party cookies.
    • Client & User ID Tracking: Lets site owners unify data across offline and online sources, respecting user consent.
    • Google Signals: Provides cross-device insights from users logged into Google, if they’ve opted into ad personalization.

3. Remarketing & Retargeting in the New Privacy Landscape

Reduced Third-Party Cookie Reliance
  • Traditional methods of tracking users who visited your site (and then showing them ads elsewhere) are hampered by the blocking of third-party cookies.
  • First-party data (e.g., email lists, logged-in user IDs) and consent-based tracking are now the backbone of effective remarketing and retargeting.

The Facebook Pixel
  • What It Is: A snippet of code placed on your website to track user actions (page views, conversions, etc.) and then retarget those users on Facebook and Instagram.

  • Changes to the Facebook Pixel:
    • Apple’s iOS 14 Update: Introduced App Tracking Transparency (ATT), limiting the data that apps and websites can collect for ad targeting.
    • Aggregated Event Measurement: Facebook now provides aggregated data when full-tracking permissions are not granted.
    • Domain Verification: Facebook requires businesses to verify their domains to control which events get priority tracking and to ensure compliance with Apple’s policies.

  • What Advertisers Need to Do:
    • Domain Verification: Follow Facebook’s instructions to prove ownership of your website domain.
    • Event Configuration: Choose and prioritize up to eight conversion events for aggregated measurement.
    • Consent Management: Ensure you’re compliant with relevant privacy regulations (GDPR, CCPA). This includes implementing a consent banner or pop-up if required.

Consent-Based Advertising
  • GDPR, CCPA, and Similar Regulations:
    • Require explicit user permission for data collection and targeting.
    • Users must opt in to tracking, which affects how remarketing or retargeting audiences are built.

Emerging Technologies
  • Google’s Privacy Sandbox:
    • Proposed solutions like FLoC (now replaced by Topics) to enable interest-based advertising without revealing individual identities.
  • Aggregated Measurement (Facebook):
    • Collects partial but privacy-compliant data, still allowing advertisers to measure the effectiveness of campaigns for consenting users.

4. Conclusion

The digital tracking landscape is undergoing a major shift as privacy regulations tighten and browsers phase out or limit third-party cookies. 

Google Analytics 4 (GA4) reflects this new reality by:

  • Emphasizing first-party cookies and event-based tracking.
  • Incorporating machine learning for filling data gaps.
  • Supporting privacy-compliant remarketing strategies reliant on user consent.

 

Meanwhile, Facebook’s Pixel has adapted to iOS updates and broader privacy changes by:

  • Introducing domain verification and aggregated event measurement.
  • Encouraging advertisers to configure their top-priority conversion events.
  • Requiring user consent to track and retarget effectively.

 

For marketers and businesses, the path forward involves:

  1. Collecting and managing first-party data responsibly.
  2. Adapting to new, privacy-focused tracking methods (GA4 event-based tracking, Facebook’s aggregated measurement).
  3. Maintaining transparent user consent practices under GDPR, CCPA, and similar regulations.

 

By proactively updating analytics and advertising strategies—while respecting user privacy—organizations can continue to glean valuable insights and maintain effective, targeted campaigns in the evolving digital ecosystem.