First-Party Domains and Server-Side Cookies: A Practical Guide for Reliable Tracking

Modern web tracking faces a fundamental challenge: browsers are increasingly blocking third-party cookies and scripts, while privacy regulations require more control over data collection. The solution? Moving to first-party domains, server-side cookies, and server-side CDPS.

This guide explains why first-party tracking is more reliable, compliant, and future-proof than traditional third-party approaches, and shows you how to implement it effectively.

What Are First-Party vs Third-Party Cookies and Domains

Understanding the Fundamental Difference

First-party cookies are set by the domain you're currently visiting. When you visit healthcare-clinic.com, any cookies set by healthcare-clinic.com are first-party cookies.

Third-party cookies are set by domains other than the one you're visiting. If you're on healthcare-clinic.com but a cookie is set by google-analytics.com, that's a third-party cookie.

How Browsers See Them Differently

Browsers treat first-party and third-party cookies with dramatically different policies:

First-Party Cookies:

• Set by default without user intervention

• Persist across browser sessions

• Survive browser privacy features

• Can be accessed by JavaScript on the same domain

• Have longer default lifespans

Third-Party Cookies:

• Blocked by default in modern browsers

• Automatically purged by browser privacy features

• Require explicit user consent in many cases

• Limited access and functionality

• Shorter lifespans due to browser restrictions

The Server-Side Advantage

Here's the critical insight: even first-party cookies aren't enough on their own. Browsers can still block JavaScript-based tracking, regardless of domain configuration. Users can disable JavaScript, use ad blockers, or browsers can simply fail to execute tracking code.

This is why server-side CDPs are becoming essential. When your website captures events (form submissions, page views, purchases) and sends them directly to your CDP and not the Third-Parties URLs.

For healthcare organizations, this is particularly important. The HHS guidance on online tracking technologies indicates that third-party scripts can create significant compliance concerns that healthcare organizations should evaluate. Server-side data collection eliminates these third-party script risks entirely.

Browser Behavior Research

Recent studies show the extent of browser restrictions on third-party cookies:

• Safari's Intelligent Tracking Prevention (ITP) currently blocks third-party cookies by default and limits their lifespan to 24 hours

• Chrome's Privacy Sandbox is phasing out third-party cookies entirely

• Firefox's Enhanced Tracking Protection blocks third-party cookies and tracking scripts

For detailed browser behavior analysis, see:

• How Different Browsers Handle First-Party and Third-Party Cookies

• First-Party vs Third-Party Cookies: The Differences from Termly

Why First-Party Matters for Compliance (State Privacy Laws + HIPAA)

The Regulatory Landscape

Healthcare organizations and businesses handling sensitive data face increasing scrutiny under both federal and state privacy laws. First-party tracking approaches can help reduce compliance risks.

HIPAA and Healthcare Data

The HHS guidance on online tracking technologies indicates that third-party scripts can create significant compliance concerns that healthcare organizations should evaluate.

How First-Party + Server-Side Helps:

• Reduced Data Leakage: No third-party scripts can help reduce risk of unintended data sharing

• Clearer Data Flow: You control exactly what data is collected and where it goes

• Audit Trail: Complete visibility into data processing activities

• Consent Management: Easier to implement granular consent controls

• Reliable Data Collection: Server-side processing isn't affected by browser restrictions or user settings

State Consumer Privacy Laws

State comprehensive privacy laws like CCPA/CPRA, Virginia's CDPA, and Colorado's CPA typically require businesses to:

• Provide clear data collection notices

• Allow users to opt-out of data sales

• Implement reasonable security measures

• Maintain accurate data inventories

First-Party + Server-Side Advantages:

• Simplified Data Inventory: All tracking happens through your domain

• Easier Opt-Out Implementation: Centralized control over data collection

• Reduced Third-Party Risk: No unexpected data sharing with external parties

• Consistent Data Quality: Server-side processing can help eliminate browser-based data loss

How Ours Privacy CDP Handles This

Server-Side Cookie and Identity Management

The Ours Privacy CDP addresses the limitations of client-side tracking by implementing First-Party server-side identity management and event dispatch:

How It Works:

1. Server-Side Cookie Setting: Cookies are set by your backend, not JavaScript

2. First-Party Domain Support: All tracking appears to come from your domain. You can configure a Custom Domain in the Ours Privacy application. This lets you load everything from our Web SDK, Google Tag Manager, the URL your events are ingested from, and even other products like Maps/Video from your own domain.

3. Persistent Identity: User identity is maintained across sessions and devices

4. Privacy Compliance: No third-party scripts or data sharing

Example

Here’s an example of Ours Privacy setting a server-side first party cookies on a configured Custom Domain. This server-side cookie is separate and different than the client side cookies we talk about above.

Custom First-Party Domain Support

Ours Privacy allows you to configure custom first-party domains so all tracking appears to originate from your own domain:

Benefits:

• Domain Consistency: All cookies and scripts appear first-party

• Brand Trust: Users see your domain, not a third-party service

• Compliance: Easier to explain data collection to users and regulators

• Performance: Faster loading without third-party script dependencies

• Reliability: Server-side processing ensures data collection works regardless of browser settings

Key Takeaways

• First-party tracking is more reliable than third-party approaches in modern browsers

• Server-side CDPs are essential for truly reliable data collection that bypasses browser restrictions

• Server-side identity management provides better persistence and control

• Custom domains make all tracking appear first-party to browsers and users

• Compliance benefits can include reduced data leakage and clearer audit trails

• Future-proofing ensures your tracking works as browsers continue restricting third-party cookies

The goal is simple: maintain reliable user tracking while respecting privacy and compliance requirements. First-party domains and server-side cookies provide the foundation for sustainable, compliant tracking in today's privacy-first web environment.

For more information on implementing these solutions, see our Customer Data Platform documentation and Custom Domains guide.

Important Disclaimers

While first-party domains and server-side tracking can help reduce certain privacy risks, compliance with applicable privacy laws (including HIPAA, CCPA, GDPR, and state privacy laws) requires careful consideration of your specific use case, data types, and legal obligations. Organizations should conduct their own privacy impact assessments and implement appropriate consent management and data protection measures. This guide is for informational purposes only and does not constitute legal or product advice.