Lexicon ID: A Promising Alternative In Cookieless World


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As digital advertising shifts toward privacy-centric practices, publishers face the challenge of monetizing their inventory without third-party cookies. In the current AdTech market, identity solutions are developing in two main directions to address the cookieless problem: probabilistic and deterministic IDs. The Lexicon, a probabilistic ID from 33Across, addresses the shortcomings of alternative solutions by providing precise results with a very high probability, enabling effective monetization of cookieless inventory by expanding the demand partner network (SSPs and DSPs) and synchronizing IDs through all the demand partners.

Deterministic IDs

Deterministic ID solutions, like LiveRamp’s IdentityLink(previously RampID) and The Trade Desk’s Unified ID 2.0, rely on authenticated user information passed from publisher websites. However, the average publisher website sees 97%–98% of anonymous visitors, which makes only a tiny part of the traffic identifiable for deterministic IDs.

Probabilistic IDs

Probabilistic ID solutions are based on information like IP address, browser version, and user-agent string. This means user identification cannot be precise due to potential data collisions (e.g., different users may come from the same IP), and ID does not contain deterministic information, like an email address. As a result, probabilistic IDs cannot guarantee the accuracy of user identification and can have collisions where multiple different users are interpreted as one. 

Both types of IDs suffer from limited partner integrations, hindering effective identification across the entire AdTech ecosystem. This is important because integration across partners allows DSPs to identify the same user during server-to-server communication, thereby increasing bid rates for ad requests. The absence of a single identifier to fully monetize traffic is a major monetary and technical issue for the market.

Why is Lexicon one step ahead of others?

Over the past few years, 33Across has been actively developing Lexicon and building a wide network of publishers and demand partners. The company focused on this task following the announcement of the impending shutdown of third-party cookies, making significant strides toward establishing Lexicon as a viable candidate for a single identifier for the AdTech ecosystem. Integrations with publishers provide more detailed user profiles, enriching ad requests during the bidding process. Numerous demand partner integrations make identification more effective during server-to-server communication, as Lexicon synchronizes user IDs with all partners, creating appropriate ID mappings for accurate user identification across systems.

Synchronization mechanisms

To maximize synchronization with partners, Lexicon employs a wide array of mechanisms:

  • Regular ID sync: Similar to the normal cookie sync process, publishers transfer user data to Lexicon through header bidding. For server-to-server communication, partners notify Lexicon of the need to sync users and transfer data through appropriate sync endpoints of Lexicon.

  • Pre-generation of IDs for new users: When a new user enters the system without a profile, Lexicon preemptively notifies partners, generates a new mapping, and passes this mapping to partners, increasing the bid rate because having any user data is preferable to having none.

  • Scheduled ID sync: Lexicon regularly exports all collected ID mappings and shares them with partners to support the largest possible overlap of IDs known to the ecosystem.

These multiple ways of synchronization make Lexicon more interconnected than many competitors.


The transition to a cookieless future presents significant challenges for publishers and advertisers. However, solutions like 33Across’s Lexicon offer a promising path forward. By combining a robust network of partners with advanced ID synchronization mechanisms, Lexicon addresses the challenge of fragmented user identification, ensuring users can be consistently identified and targeted across the entire network, enhancing the effectiveness and precision of ad targeting, and making Lexicon a viable candidate for a single identifier in the AdTech ecosystem.

Learn more about Lineate’s custom solutions for AdTech


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