For more than twenty years, third-party cookies were the main mechanism that sustained the economic model of digital advertising on the Internet. Thanks to them, advertisers, advertising technology platforms, and media networks were able to track the behavior of millions of users while they browsed across different websites. This tracking made it possible to build extremely detailed audience profiles, measure conversions, run remarketing campaigns, and optimize advertisements automatically. Without cookies, a large part of the programmatic advertising infrastructure simply would not have existed.
However, the system began to face increasingly strong criticism. Regulators, privacy experts, and users started questioning the enormous amount of information collected without a clear understanding by individuals. Cross-site tracking became one of the most sensitive issues within the modern digital ecosystem, especially after the implementation of regulations such as the European GDPR and the CCPA in the United States. At the same time, browsers such as Safari and Firefox began aggressively blocking third-party cookies, while Google announced the gradual elimination of that mechanism in Chrome.
The advertising industry quickly understood that a historic transformation was approaching. The problem was not only technical, but structural: if the central mechanism for user identification disappeared, fundamental functions such as audience segmentation, advertising frequency control, campaign measurement, and conversion attribution would also be affected. In this context, the so-called universal identity solutions emerged, whose objective was to rebuild the digital identification system without directly depending on third-party cookies.
Among all the initiatives that appeared on the market, two projects began to stand out because of their level of adoption and technological ambition: ID5 and Unified ID 2.0, commonly known as UID 2.0. Both platforms represent some of the most important attempts to redefine the identity infrastructure of the open web.
What are universal identity solutions really?
Universal identity solutions are systems designed to recognize digital users persistently across different platforms, devices, and advertising environments, but using mechanisms different from traditional cookies. The main function of universal identity solutions is to allow digital advertising to continue being personalized and measurable even in an environment where the browser no longer allows classic tracking based on third-party cookies. Today, universal identity solutions have become one of the most important technical pillars of modern programmatic advertising.
Unlike traditional cookies, universal identity solutions do not depend exclusively on a file stored by a third party inside the browser. Instead, these universal identity solutions use a much more sophisticated combination of identity signals to build persistent identifiers shared across platforms. Among the technologies used by universal identity solutions are authenticated data such as email addresses, first-party identifiers provided by websites themselves, contextual device information, probabilistic models, and cryptographic systems capable of generating interoperable identity layers.
The logic behind universal identity solutions is relatively simple to understand from a commercial perspective. Advertising companies still need to recognize users in order to maintain basic digital marketing capabilities, and universal identity solutions make it possible to preserve a large part of those functions without depending on third-party cookies. Without a consistent identity, programmatic advertising loses much of its economic efficiency. Advertisers would no longer be able to know whether a user previously saw an advertisement, purchased a product after a campaign, or belongs to a specific audience with certain interests.
For that reason, universal identity solutions attempt to build a new interoperable identification layer for the entire open web. Instead of depending exclusively on the browser, universal identity solutions create shared identity resolution systems capable of operating across multiple devices and digital channels, including mobile applications, streaming, connected television, and digital audio platforms. Thanks to this approach, universal identity solutions became consolidated as the most important technical replacement for third-party cookies within the modern advertising ecosystem.
UID 2.0 and the reconstruction of advertising identity
Unified ID 2.0 emerged as one of the most ambitious initiatives in the entire advertising industry following the decline of third-party cookies. UID 2.0 was initially driven by The Trade Desk and quickly received support from numerous companies within the adtech ecosystem interested in finding a viable alternative for advertising tracking. Since its appearance, UID 2.0 positioned itself as one of the most important universal identity solutions within the transformation of modern digital advertising.
The central idea behind UID 2.0 consists of using authenticated data provided directly by users, mainly email addresses or phone numbers, to generate encrypted identifiers that can be used within programmatic advertising. When a person logs into a participating website and agrees to share their data for advertising purposes, UID 2.0 transforms that information through cryptographic hashing and encryption processes. The result is a secure identifier that can be used for targeting, measurement, and attribution without directly exposing the original personal information. Thanks to this approach, UID 2.0 became consolidated as one of the most relevant universal identity solutions for replacing cookie-based tracking.
This approach represents an important difference compared to the historical functioning of cookies. Third-party cookies depended completely on the browser and on the ability of an external company to store identifiers on the user’s device. UID 2.0, by contrast, relies on authenticated relationships between users and publishers. Identity is no longer built only from the browser, but from registered accounts and explicit consent. For this reason, many companies consider UID 2.0 one of the most advanced universal identity solutions from both a regulatory and technological perspective.
One of the most important aspects of the UID 2.0 model is that it incorporates control and transparency mechanisms designed to adapt to new regulatory requirements. The system includes opt-out tools, token rotation, advanced encryption, and periodic identifier expiration. The intention of UID 2.0 is to create an identity infrastructure capable of sustaining personalized advertising without exactly replicating the opaque practices historically associated with third-party cookies. In the current context, UID 2.0 represents one of the most visible examples of how universal identity solutions attempt to balance advertising personalization and privacy.
Additionally, UID 2.0 was designed from the beginning to function beyond the traditional web. The platform seeks to operate in mobile applications, connected TV environments, streaming, and other digital formats where cookies were never particularly effective. This omnichannel vision is one of the elements explaining the industry’s growing interest in universal identity solutions such as UID 2.0, especially in sectors linked to streaming and connected television.
The importance of authenticated data
The growth of UID 2.0 reflects a much deeper change within the Internet: the transition toward an ecosystem increasingly based on authenticated users. For many years, a huge number of websites allowed browsing without registration. However, the disappearance of third-party cookies radically changed publishers’ economic incentives and accelerated the adoption of universal identity solutions based on first-party data.
In the new advertising landscape, having registered users became extremely valuable. A website capable of obtaining visitors’ email addresses can generate persistent identifiers that are much more stable and useful for the modern advertising ecosystem. For that reason, strategies to encourage user registration began multiplying, even among media outlets that historically operated with completely open access. This change greatly strengthened the role of universal identity solutions within programmatic advertising.
Newsletters, membership programs, free registrations, and soft paywalls became strategic tools to strengthen first-party data. Email stopped being simply a means of contact and became a central piece of the new digital identity infrastructure. Consequently, universal identity solutions began to depend increasingly on authenticated relationships between users and publishers.
This phenomenon also produced important changes in the distribution of power within the advertising ecosystem. Large publishers with millions of authenticated users gained significant competitive advantages compared to small media outlets or sites that lack direct relationships with their audiences. In many ways, the transition toward universal identity solutions models favors platforms capable of building closed ecosystems of registered users and strong bases of first-party data.
ID5 and the hybrid approach to digital identity
While UID 2.0 was primarily oriented toward authenticated identities based on email addresses, ID5 developed a more flexible and technically hybrid approach. ID5 positioned itself as an independent identity solution for the open web, especially focused on the programmatic advertising ecosystem. Within the universal identity solutions market, ID5 gained relevance due to its ability to operate even in environments with lower levels of authentication.
The objective of ID5 is to generate persistent identifiers capable of functioning even in contexts where explicit user authentication does not exist. To achieve this, ID5 combines deterministic and probabilistic signals through advanced machine learning systems and identity resolution techniques. Thanks to this architecture, ID5 became one of the most flexible universal identity solutions in the modern advertising industry.
Deterministic signals are those that allow a user to be identified with a high degree of certainty, such as a registered email or an authenticated login. Probabilistic signals, on the other hand, use inferences based on technical device characteristics, IP address, browser, browsing behavior, and other digital patterns. Through algorithmic models, ID5 attempts to estimate the probability that different interactions belong to the same person or device. This hybrid approach differentiates ID5 from other universal identity solutions focused exclusively on authentication.
ID5’s probabilistic approach is especially important because a large part of the Internet still operates without mandatory authentication. Many users simply do not want to register on every site they visit. ID5 attempts to solve that problem by creating an identity layer that can operate even in the absence of permanent login. Thanks to this, ID5 has positioned itself as one of the most adaptable universal identity solutions for the open web.
The company also developed sophisticated identity graphs capable of connecting multiple identifiers related to a single person or digital household. These identity graphs allow linking mobile devices, browsers, applications, and connected televisions within a unified view of the user. Thanks to this, ID5 can maintain advertising functions such as cross-device frequency control and multi-channel attribution. These capabilities explain why universal identity solutions like ID5 have become so important in the evolution of programmatic advertising after third-party cookies.
What is an identity graph and why is it so important?
The concept of an identity graph became one of the fundamental pillars of modern digital advertising and the growth of universal identity solutions. An identity graph is essentially a large relational database designed to connect different digital identifiers that belong to the same individual, household, or related set of devices. Within the current ecosystem of universal identity solutions, identity graphs play a key role because they allow identity signals from multiple platforms and digital channels to be unified.
In the modern digital ecosystem, a single person can interact daily through multiple environments: smartphone, laptop, smart TV, mobile applications, web browser, and streaming platforms. Each of these channels generates different identifiers and massive amounts of fragmented data. The challenge for advertising companies and for universal identity solutions is to understand which of these identifiers actually belong to the same user. Without this ability to connect signals, many essential programmatic advertising functions would lose effectiveness.
Identity graphs attempt to solve exactly that problem. Using statistical models, deterministic signals, and advanced machine learning systems, universal identity solutions can build relationships between seemingly independent devices. In this way, an advertising platform can understand that the person who saw an advertisement on connected TV is likely the same person who later visited an online store from their mobile phone. Thanks to this capability, universal identity solutions have managed to replace a large part of the historical functions of third-party cookies.
This capability is extremely valuable for advertisers because it allows them to maintain a consistent advertising experience across platforms and devices. In addition, identity graphs facilitate campaign measurement, frequency control, and conversion attribution in an increasingly fragmented digital environment. As a result, universal identity solutions increasingly rely on sophisticated identity resolution systems to sustain personalized advertising within the open web.
The transition from third-party cookies to universal identity solutions represents one of the most important changes in the history of digital advertising. For years, the browser was the absolute center of the online advertising infrastructure, and cookies functioned as the main mechanism for identifying users within the open web. Today, however, the industry is moving toward distributed systems of interoperable identity where universal identity solutions enable essential functions such as targeting, attribution, and measurement beyond the traditional browser.
This change has deep implications for the entire digital ecosystem and for the future of programmatic advertising. First-party data becomes extremely valuable, authentication becomes fundamental, and direct relationships between publishers and users move to the center of the advertising economy. In this new scenario, universal identity solutions are consolidated as key tools for connecting devices, platforms, and digital channels within a shared identity infrastructure. At the same time, companies capable of building large identity graphs and advanced identity resolution systems gain increasingly significant competitive advantages.
ID5 and UID 2.0 symbolize precisely this new stage of technological evolution. These universal identity solutions are not simple technical replacements for third-party cookies, but entirely new architectures designed to sustain personalized advertising in a much more complex, regulated, and fragmented environment. Both UID 2.0 and ID5 reflect how universal identity solutions are redefining the way the industry builds audience profiles, measures advertising campaigns, and connects users across multiple devices and digital platforms.
The disappearance of third-party cookies did not eliminate the commercial need to identify digital users. What it did was force the entire industry to completely redesign how identity is built, shared, and managed across the Internet. In this process, universal identity solutions have become one of the most important technological pillars of the new advertising web and will likely continue evolving over the coming years as regulatory demands, device fragmentation, and user privacy expectations continue to increase.
Understanding how universal identity solutions work, how platforms like ID5 and UID 2.0 operate, and what their technical and regulatory implications are will be essential for any company involved in digital advertising, programmatic marketing, audience monetization, or first-party data strategies. The future of digital advertising will largely depend on companies’ ability to adapt to this new ecosystem of interoperable and omnichannel identity.
If your company is looking to adapt to this new stage of digital advertising, implement advanced first-party data strategies, or better understand how universal identity solutions work, at MoodWebs we can help you. Our team works on digital strategies, advertising technology, analytics, and solutions focused on the evolution of the modern programmatic ecosystem. For more information about our services, you can write to [email protected] and learn how MoodWebs can help your business prepare for the future of digital identity and advertising on the open web.
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