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As third-party identifiers fade across Europe and measurement grows harder, the difference between brands that grow and those that stall increasingly comes down to how well they understand, connect and activate their customer data.
This guide explains the four core data types — first-, second-, third- and zero-party data — and, more importantly, how they work together in a modern, privacy-first data strategy.
For years, marketers relied on third-party cookies and probabilistic identifiers to fill the gaps in their understanding of customers. That model is no longer viable, if it ever truly was.
The result is not a shift away from data but a shift towards owned, consented and connected data. Understanding the role each data type plays is the foundation of that shift.
First-party data is information a brand collects directly from customers through its own channels. It is the most reliable and strategically valuable data asset because it is gathered with consent, owned outright, and rooted in real interactions and transactions.
Typical sources include:
This data is collected directly from consumers, transactions and by placing a pixel on your website, mobile app, product or social channels. Typically, the information is recorded in a customer relationship manager (CRM) or digital management platform (DMP).
Why is first-party data important?
What makes first-party data powerful is not volume, but continuity. It allows brands to recognise customers across sessions, devices and moments, rather than treating each interaction in isolation. In an environment where customers routinely use multiple devices, email addresses or payment methods, first-party data provides the strongest anchor for identity.
It drives cross-sell and upsell opportunities.
You can use this data to tailor your messages to their needs and wants, like which categories they recently purchased from. information is used to personalise offers and messaging to entice them to buy again, explore accessory items and try alternatives they might like.
It can futureproof your marketing.
Because first-party data is collected by you from your website, it has staying power a cookie does not. However, collecting this data is rarely the limiting factor. The challenge is resolving it into a single customer view that can be activated consistently across channels and used to measure real outcomes, not just engagement.
Second-party data is another organisation’s first-party data, shared or activated through a direct partnership. In practice, it often looks identical to first-party data in structure and quality, but differs in ownership.
Second-party data commonly comes from:
Why is second-party data important?
Second-party data is a great way to expand the scope of your data while ensuring accuracy and relevancy. With an increased reach, you can start to engage other potential prospects that you may not have had access to in the past.
For certain verticals, such as CPG, partnering with retailers allows brands who don’t hold a direct relationship with the customer to measure the performance of campaigns and what consumers go on to buy.
It (also) future-proofs your marketing.
In European markets, retail media has become one of the most important second-party data channels, enabling brands to connect media exposure to in-store and online purchases while remaining within clear consent and governance frameworks.
Third-party data is data you buy from an outside source that is not the original collector of said data. It can come from a wide variety of sources both offline and across the digital ecosystem. Historically, it played a central role in prospecting and audience expansion, particularly through cookie-based targeting.
It typically includes:
Why is third-party data important?
The primary benefit of third-party data is to beef up the data you already have and widen your scope of people to target. Most brands will purchase third-party data to add critical demographic information to customer profiles to help improve personalisation.
It helps you discover best prospects.
Through modelling and advanced analytics, third-party data can be used to identify your current best customers and find more potential customers who look just like them. These prospects can be reached across all channels, including digital, advanced TV, email, direct mail, digital out of home, audio and gaming.
It is NOT necessarily futureproof
In 2026, the role of third-party data has narrowed. Used sparingly and strategically, it can add dimensionality but the brands that struggle most with third-party data will be those using it to compensate for weak first-party foundations.
When choosing a data partner, it’s important to carefully vet them to ensure they follow data and privacy best practices. Third-party data can then be purchased as audience segments for individual campaigns, meaning you can choose exactly which kind of customer you want to reach.
Zero-party data is voluntarily and proactively shared by the customer with a brand. It often includes preferences, purchase intentions, personal contexts and data on how the individual wants to be treated by the brand.
Zero-party data consists of:
Why is zero-party data important?
What distinguishes zero-party data is intent. Customers are not being observed; they are speaking. This makes it particularly valuable for personalisation and experience design. While self-reporting can sometimes be an issue, for the most part, you have to trust what your customers are telling you.
It's (even more) privacy protected.
With GDPR and CCPA regulations, marketers should prioritise collecting data their audiences are consciously giving them.
It makes personalisation that much better.
Using zero-party data capture techniques like interactive quizzes and games gives you the opportunity to dynamically enhance and personalise content in real-time.
Understanding these four categories is necessary, but insufficient. Competitive advantage does not come from collecting more types of data; it comes from connecting them meaningfully.
Modern data strategies focus on resolving identity across touchpoints, unifying online and offline interactions, and enabling transaction-level measurement. When first-party data is connected at the person level and selectively enhanced with zero-, second- and third-party inputs, brands gain a more accurate picture of who their customers are and how value is created over time.
The loss of third-party cookies did not create a data problem. It exposed one.
With a weaker connective layer such as third-party cookies, brands tend to overexpose the same individuals, misread incremental performance, and rely on last-click attribution that overvalues bottom-funnel activity. Measurement becomes distorted, and costs rise as reach stagnates.
Brands that adapt successfully treat identity as infrastructure rather than a media tactic. They link web, app, CRM and transaction data into a governed, consented customer view that supports both activation and measurement.
When customer data is properly connected, marketing becomes more coherent. Messaging is more consistent, frequency is controlled, reach is extended incrementally, and performance is measured against outcomes rather than proxies.
This enables closed-loop marketing, where insights from one campaign directly inform the next, and where acquisition, retention and lifetime value are measured on the same foundation.
Epsilon works with European brands to build privacy-first data strategies grounded in first-party data, identity resolution and transaction-level measurement. Our platforms and services help brands move from fragmented signals to connected customer understanding, enabling more effective activation and more credible measurement across the customer lifecycle.
From Epsilon Digital to Epsilon Retail Media, our suite of products and services are backed by decades of industry expertise and are designed to help your business reach its marketing goals.
