The End of Third-Party Cookies

What it Means and How to Respond - Moving Away from Opaque Collection and Use of Consumer Data Towards a Decision-Oriented, Transparent, and Privacy-Friendly Future.

The internet is at a turning point. Google has announced the phasing out of third-party cookies, with Apple planning to follow suit. Given that Chrome and Safari account for about 80 percent of the global market share, this has significant implications for the online world. However, to fully grasp the impact of this announcement, we first need to explain what cookies are and the different types that exist.

What are Cookies?

A cookie is a small text file stored in a browser used to access the internet. Most people have hundreds of cookies saved on their devices. The primary purpose of a cookie is to identify users and possibly create customized web pages or store login information for a website. Since a web server has no memory, the hosted website a user visits sends a cookie file to the browser, which is stored on the computer's hard drive. This allows the website to remember the user and their preferences. This exchange of information enables the web server to use this data to present customized web pages to the user.

Cookies are thus highly useful as they allow modern websites to function as people expect, with an increasing level of personalization and extensive interactive features. This targeted use of cookies is what legislation aims to highlight. By requiring websites to inform their visitors and obtain consent, internet users are given more control over their online privacy.

Different Types and Uses of Cookies and Data

One of the most important attributes of a cookie is its "host" — the domain name of the website that ultimately sets the cookie. Only the host domain can retrieve and read the cookie's content once set. If the host name matches the domain in the browser's address bar when the cookie is set or retrieved, it is a first-party cookie. In the context of advertising, first-party data belongs to the company itself.

If the host domain of a cookie does not match the one displayed in the browser bar when downloaded, it is a third-party cookie. Third-party data is provided by third parties who either collect or purchase data. To collect data, third parties typically use cookies to tag and track users across various websites.

There are also second-party data, which involve sharing or purchasing data from a "trusted partner." In the context of large B2C companies with multiple brands, second-party data can simply be the sharing of first-party data of one brand with another. Second-party data are externally collected first-party or partner data. This means the data primarily come from strategic partnerships or campaign data providing information about behavior, environment, technical conditions, or the number and duration of ad consumption. The data are collected by an external source (ad server, DMP, etc.). The sharing of external data by partners is usually contractually agreed upon (sharing model).

Impact of Third-Party Cookie Removal

The deprecation of third-party cookies represents one of the most significant shifts in digital advertising since the rise of programmatic buying. For years, the online advertising ecosystem relied on these cookies to enable cross-site tracking, retargeting, and audience segmentation at scale. Their removal directly affects several key capabilities:

Audience targeting: Behavioral targeting based on browsing history across multiple websites becomes impossible without third-party cookies. Advertisers lose the ability to reach users who visited competitors' sites or browsed specific product categories elsewhere.

Frequency capping: Without a common identifier across sites, preventing users from seeing the same ad too many times becomes technically challenging — affecting both user experience and advertising efficiency.

Conversion attribution: Multi-touch attribution models that track a user's journey from first exposure to final conversion across multiple websites require cross-site tracking. The loss of third-party cookies forces a fundamental rethink of attribution methodology.

Lookalike audiences: The rich behavioral profiles built from third-party data fueled lookalike modeling. Without this data source, the fidelity of these models decreases significantly.

The impact is not uniform across industries. Publishers who monetize through programmatic advertising face direct revenue pressure, while direct-to-consumer brands with strong first-party data assets may find themselves at a competitive advantage.

Alternative Tracking and Targeting Methods

In response to the third-party cookie sunset, the industry has developed several privacy-preserving alternatives:

Contextual targeting: Rather than targeting users based on behavioral history, contextual advertising matches ads to the content of the page being viewed. A user reading about travel destinations sees travel-related ads regardless of their historical browsing behavior. This approach is inherently privacy-safe and has seen a significant renaissance.

Server-side tracking: By moving tracking logic from the browser to the server, organizations can collect and process data without relying on browser-based cookies. This provides greater control and resilience against browser restrictions.

Privacy-enhancing technologies (PETs): Google's Privacy Sandbox initiative introduced proposals like the Topics API, which enables interest-based advertising without exposing individual browsing histories. These approaches aim to provide utility to advertisers while protecting individual user privacy.

Identity resolution: Email-based identity matching using hashed email addresses allows advertisers and publishers to connect data across platforms while maintaining user privacy. These solutions are particularly effective when users are authenticated, making subscription and consent management a critical enabler.

Universal IDs: Industry initiatives like Unified ID 2.0 create persistent, privacy-compliant identifiers based on authenticated user data rather than browser state.

First-Party Data and Identity-Based Solutions

The shift away from third-party cookies accelerates the strategic importance of first-party data — information collected directly from users through their authenticated interactions with your platforms. Unlike third-party data, first-party data is:

• Consented: Users have explicitly agreed to share their data, creating a transparent and compliant data relationship
• Accurate: It reflects actual behavior on your own platforms rather than inferred characteristics
• Durable: It is not subject to browser restrictions or platform policy changes
• Differentiating: Your first-party data is unique and cannot be purchased by competitors

Building a robust first-party data strategy requires the right identity infrastructure. A Single Sign-On solution enables users to authenticate once and interact across all your digital touchpoints, creating a unified view of each user. This authenticated relationship becomes the foundation for all first-party data collection.

White-label identity management platforms go further by enabling organizations to build persistent user profiles enriched with zero-party data — information users actively and voluntarily share, such as preferences, interests, and purchase intent. When users log in through OpenID Connect or federated identity protocols, every interaction enriches their profile, creating increasingly accurate personalization without privacy risks.

Digital Marketing in a Cookieless World

The cookieless future demands a fundamental shift in marketing strategy — from mass targeting based on behavioral surveillance to relationship-based marketing built on consent and value exchange. Organizations that treat this transition as a compliance burden will struggle; those who see it as an opportunity to build deeper customer relationships will thrive.

Invest in authentication: Every authenticated user is worth significantly more than an anonymous visitor. Encouraging registration through value exchange — exclusive content, personalized experiences, loyalty benefits — converts anonymous traffic into addressable audience members.

Build consent as a competitive advantage: Transparent data practices and genuine value exchange create trust that translates into higher consent rates and richer data. A well-designed consent and newsletter management system turns passive visitors into active data partners.

Rethink measurement: Last-click attribution is already insufficient; in a cookieless world, it becomes unreliable. Invest in marketing mix modeling, incrementality testing, and panel-based measurement to understand true campaign effectiveness.

Leverage contextual signals: Content strategy becomes targeting strategy. If your content attracts the right audience, contextual advertising can reach them effectively without cross-site tracking.

The social media monetization gap that many organizations face — having large audiences on rented platforms but lacking owned, addressable user data — is directly addressed by building robust first-party data infrastructure now.

The AD Market is Changing. Zero- and First-Party Data are the Future.

As the industry loses access to most third-party data, the ability to target and measure will be impacted. Privacy protection and control over personal data will take center stage. Companies must not only collect and use data responsibly but also ensure that their efforts are visible to customers. Marketers often describe the advantage of first-party data over third-party data as the ability to target customers based on verified information.

Advertisers and publishers must now primarily rely on their own zero/first-party data or data from walled gardens, contextual targeting, and greater support from data platforms. This reliance on zero/first-party data requires the development of an internal data privacy strategy.

With Unidy, we enable companies to collect, centralize, and monetize first-party user data by seamlessly connecting individual service silos through a central user account and single sign-on. If you would like to implement your zero/first-party data strategy with Unidy, please contact us.