Third-party cookies are already dead in Safari and Firefox. Chrome still holds 65% of browser market share, but the writing is on the wall: the future of digital marketing belongs to those who master first-party data. In this guide, I’ll share practical strategies I’ve developed over 15 years working with companies like Deliveroo, Barclays, and Tesco to help you build a sustainable data strategy.

Whether Google eventually deprecates cookies or not, the shift to first-party data isn’t optional—it’s essential. Privacy regulations are tightening, user expectations are changing, and the brands that thrive will be those that build direct relationships with their audiences.

What is First-Party Data (And Why It Matters Now)

Before diving into strategy, let’s clarify what we’re talking about. Data comes in three flavours:

Type	Definition	Example
First-Party Data	Data you collect directly from your audience	Purchase history, website behaviour, email engagement
Zero-Party Data	Data users intentionally share with you	Preferences, survey responses, quiz answers
Third-Party Data	Data collected by external sources	Cookie-based tracking across websites, purchased lists

The critical difference: first-party and zero-party data are yours. You own it, you control it, and—crucially—you collected it with consent. Third-party data? You’re renting it, and that rental agreement is expiring.

Here’s the reality in 2025: Safari’s Intelligent Tracking Prevention and Firefox already block third-party cookies by default. That’s roughly 35% of web traffic operating in a cookieless environment today. Even if Chrome never removes cookies, building your strategy around borrowed data is like building your house on rented land.

The Business Case for First-Party Data

This isn’t just about compliance—it’s about competitive advantage. When I led the analytics team at Barclays, we rebuilt our marketing attribution using first-party data. The result? We identified £2.3 million in wasted ad spend that third-party tracking had attributed incorrectly.

First-party data delivers three key advantages:

• Accuracy: Data collected directly from your users is inherently more reliable than inferred data from third parties
• Compliance: With GDPR, CCPA, and emerging privacy laws, consent-based collection protects your business
• Ownership: Your data strategy doesn’t depend on Google’s product decisions or browser policies

At Deliveroo, we built our entire customer analytics infrastructure on first-party data. When iOS 14.5 introduced App Tracking Transparency and decimated third-party mobile attribution, our measurement capabilities remained intact. Competitors scrambled; we continued optimising.

Building Your Data Collection Framework

Effective first-party data collection rests on three pillars: value exchange, collection points, and consent management.

Value Exchange: What Users Get

Users won’t share data for nothing. Every collection point needs a clear value proposition:

• Account creation: Access to order history, saved preferences, faster checkout
• Newsletter signup: Exclusive content, early access, discounts
• Preference centre: Personalised recommendations, relevant communications
• Loyalty programme: Points, rewards, member-only benefits

The exchange must feel fair. At Tesco, we found that customers who understood exactly how their data improved their experience were 3x more likely to opt in to data collection.

Collection Points: Where to Gather Data

Map every touchpoint where you can collect first-party data:

Touchpoint	Data Type	Value Exchange
Registration	Email, name, preferences	Account benefits
Purchase	Transaction data, product interests	Order tracking, recommendations
Support	Issues, feedback, satisfaction	Better service
Content	Topic interests, engagement	Relevant content
Surveys	Preferences, opinions	Product improvements

Consent Management: Doing It Right

Consent isn’t a checkbox—it’s a relationship. The ICO’s guidance on cookies makes clear that valid consent must be freely given, specific, informed, and unambiguous. Best practices I’ve seen work:

• Be specific: Explain exactly what you’re collecting and why
• Make it granular: Let users choose what to share
• Easy opt-out: If users can’t leave easily, they won’t join willingly
• Regular refresh: Re-confirm consent periodically

Technical Implementation: Data Layer Architecture

Here’s where many guides stop—but this is where real value begins. A proper data layer is the foundation of any serious first-party data strategy.

A data layer is a JavaScript object that sits between your website and your analytics tools. It standardises how data is collected and shared, making your tracking more reliable and easier to maintain. The Google Tag Manager documentation provides excellent guidance on implementation.

Here’s a basic structure:

window.dataLayer = window.dataLayer || [];
dataLayer.push({
  'event': 'page_view',
  'page_type': 'product',
  'user_status': 'logged_in',
  'user_id_hashed': 'abc123def456',
  'content_group': 'electronics'
});

For e-commerce, extend this with transaction data:

dataLayer.push({
  'event': 'purchase',
  'transaction_id': 'T12345',
  'value': 99.99,
  'currency': 'GBP',
  'items': [{
    'item_id': 'SKU001',
    'item_name': 'Wireless Headphones',
    'price': 99.99,
    'quantity': 1
  }]
});

Server-side tracking takes this further. Instead of sending data from the browser (where ad blockers can interfere), you send it from your server. This improves data accuracy significantly—we saw a 15-20% increase in tracked conversions at Deliveroo after implementing server-side tracking.

Tools like Google Tag Manager Server-Side, Segment, or Tealium can handle this, routing data to your analytics platforms without relying on client-side cookies.

Activating First-Party Data Across Channels

Collecting data is pointless if you don’t use it. Here’s how to activate first-party data across your marketing channels.

Email Personalisation

Email remains the highest-ROI channel for most businesses, and first-party data supercharges it:

• Segment by purchase history and browsing behaviour
• Trigger emails based on specific actions (abandoned cart, product views)
• Personalise content based on stated preferences

On-Site Experience

Use first-party data to personalise the website experience:

• Product recommendations based on browsing history
• Dynamic content based on user segment
• Returning visitor recognition and tailored messaging

Paid Media Activation

First-party data feeds directly into advertising platforms:

• Customer Match (Google): Upload hashed email lists for targeting and exclusion
• Custom Audiences (Meta): Create lookalike audiences from your best customers
• Conversions API: Send conversion data server-side for better attribution

The key insight: first-party data makes your paid media more efficient by improving both targeting and measurement.

Tools and Platforms for First-Party Data

The right tools depend on your scale and complexity. Here’s my assessment based on implementing these across various organisations:

Tool	Best For	Starting Price
Segment	Startups to mid-market, clean API	Free tier available
Tealium	Enterprise, complex requirements	Custom pricing
mParticle	Mobile-first businesses	Custom pricing
Mixpanel	Product analytics, SaaS	Free tier available
Amplitude	Product analytics, larger scale	Free tier available
Rudderstack	Open-source alternative to Segment	Free tier available

For most businesses starting out, I recommend Segment or Rudderstack for data collection, paired with Mixpanel or Amplitude for analysis. This gives you a solid foundation without enterprise-level costs.

Measuring Success: KPIs That Matter

You can’t improve what you don’t measure. Track these metrics to assess your first-party data strategy:

Metric	What It Measures	Target
Identified User Rate	% of visitors with known identity	30-50% for e-commerce
Consent Rate	% accepting data collection	70%+ with good UX
Data Completeness	% of profiles with key fields	80%+ for active users
Match Rate	% matched in ad platforms	50-70% is strong
Attribution Accuracy	Conversion tracking reliability	Compare to baseline

Review these monthly. At Barclays, we built dashboards specifically tracking first-party data health, which helped us identify collection gaps before they impacted campaign performance.

Common Mistakes to Avoid

After implementing first-party data strategies across multiple organisations, I’ve seen these mistakes repeatedly:

1. Collecting without activating: Data sitting in a warehouse creates no value. Build activation use cases before expanding collection.
2. Ignoring data quality: Duplicate records, inconsistent formats, and outdated information poison your insights. Invest in data hygiene.
3. Over-complicating consent: Complex consent flows kill conversion rates. Keep it simple and transparent.
4. Siloed data: First-party data spread across disconnected systems can’t deliver personalisation. Unify your customer view.
5. No value exchange: Asking for data without offering something in return feels extractive. Always lead with user benefit.

Frequently Asked Questions

Is first-party data really necessary if Google keeps cookies?

Yes. Even if Chrome never removes cookies, Safari and Firefox already block them—that’s 35% of users. Plus, privacy regulations and user expectations are shifting regardless of Google’s decisions. Building on first-party data future-proofs your business.

How long does it take to build a first-party data strategy?

A basic implementation takes 2-3 months: data layer setup, consent management, and initial activation. A mature strategy with advanced personalisation typically takes 6-12 months. Start small, prove value, then expand.

What’s the difference between a CDP and a DMP?

A Customer Data Platform (CDP) focuses on first-party data and builds persistent customer profiles. A Data Management Platform (DMP) traditionally handled third-party cookie data for advertising. As cookies decline, CDPs are becoming the standard while DMPs are evolving or becoming obsolete.

Can small businesses implement first-party data strategies?

Absolutely. You don’t need enterprise tools. Start with basics: email collection with clear value exchange, a simple data layer using Google Tag Manager, and Mixpanel or Amplitude’s free tiers for analysis. Scale your tooling as your needs grow.

How do I measure ROI on first-party data investment?

Track three areas: improved attribution accuracy (reduced wasted spend), higher email/personalisation performance (increased revenue), and reduced dependency on third-party data costs. Most organisations see positive ROI within 6-12 months.

Getting Started: Your Next Steps

Building a first-party data strategy doesn’t require a massive transformation. Start with these steps:

1. Audit your current state: Where are you collecting first-party data today? Where are the gaps?
2. Implement a data layer: Even a basic one improves data quality immediately
3. Review consent flows: Are you making it easy for users to understand and agree?
4. Pick one activation use case: Email personalisation is often the quickest win
5. Measure and iterate: Track your KPIs and continuously improve

The cookieless future isn’t coming—for many users, it’s already here. The businesses that invest in first-party data now will have a significant advantage over those still scrambling to adapt.

If you’re looking to discuss your specific situation, feel free to reach out at [email protected].