
2024 marked a significant year. AI became integral to our workflows, commerce and retail media networks soared, and Google did not deprecate cookies. Amidst these changes, ID bridging emerged as a hot topic, raising questions around identity reliability and transparency, which necessitated industry-wide standards. We believe the latest IAB OpenRTB specifications, produced in conjunction with supply and demand-side partners, set up the advertising industry for more transparent and effective practices.
So, what exactly is ID bridging?
As signals, like third-party cookies, fade, ID bridging emerged as a way for the supply-side to offer addressability to the demand-side. ID bridging is the supply-side practice of connecting the dots between available signals, that were generated in a way that is not the expected default behavior, to understand a user’s identity and communicate it to prospective buyers. It enables the supply-side to extend user identification beyond the scope of one browser or device.

Imagine you visit a popular sports website on your laptop using Chrome. Later, you use the same device to visit the same sports website, but this time, on Safari. By using identity resolution tools, a supply-side partner can infer that both visits are likely from the same user and communicate with them as such.
ID bridging is not inherently a bad thing. However, the practice has sparked debate, as buyers want full transparency into the use of a deterministic identifier versus an inferred one. This complicates measurement and frequency capping for the demand-side. Before OpenRTB 2.6, ID bridging led to misattribution as the demand-side could not attribute ad exposures, which had been served to a bridged ID, to a conversion, which had an ID different from the ad exposure.
OpenRTB 2.6 sets us up for a more transparent future
In 2010, the IAB, along with supply and demand-side partners, formed a consortium known as the Real-Time Bidding Project for companies interested in an open protocol for the automated trading of digital media. The OpenRTB specifications they produced became that protocol, adapting with the evolution of the industry.
The latest evolution, OpenRTB 2.6, sets out standards that strive to ensure transparency in real-time bidding, mandating how the supply-side should use certain fields to more transparently provide data when inferring users’ identities.
What’s new in OpenRTB 2.6?
Here are the technical specifications for the industry to be more transparent when inferring users’ identities:
- Primary ID field: This existing field now can only contain the “buyeruid,” an identifier mutually recognized and agreed upon by both buyer and seller for a given environment. For web environments, the default is a cookie ID, while for app activity, it is a mobile advertising ID (MAID), passed directly from an application downloaded on a device. This approach ensures demand-side partners understand the ID’s source.
- Enhanced identifier (EID) field: The EID field, designated for alternative IDs, now accommodates all other IDs. The EID field now has additional parameters that provide buyers transparency into how the ID was created and sourced, which you can see in the visual below:

Using the above framework, a publisher who wants to send a cross-environment identifier that likely belongs to the same user would declare the ID as “mm=5,” while listing the potential third-party identity resolution partner under the “matcher” field, which the visual below depicts. This additional metadata gives the demand-side the insights they need to evaluate the reliability of each ID.

“These updates to OpenRTB add essential clarity about where user and device IDs come from, helping buyers see exactly how an ID was created and who put it into the bidstream. It’s a big step toward greater transparency and trust in the ecosystem. We’re excited to see companies already adopting these updates and can’t wait to see the industry fully embrace them by 2025.”
Hillary Slattery, Sr. Director, Programmatic, Product Management, IAB Tech Lab
Experian will continue supporting transparency
As authenticated signals decrease due to cookie deprecation and other consumer privacy measures, we will continue to see a rise in inferred identifiers. Experian’s industry-leading Digital Graph has long supported both authenticated and inferred identifiers, providing the ecosystem with connections that are accurate, scalable, and addressable. Experian will continue to support the industry with its identity resolution products and is supportive of the IAB’s efforts to bring transparency to the industry around the usage of identity signals.
Supply and demand-side benefits of adopting the new parameters in OpenRTB 2.6
- Partner collaboration: Clarity between what can be in the Primary ID field versus the EID field provides clear standards and transparency between buyers and sellers.
- Identity resolution: The supply side has an industry-approved way to bring in inferred IDs while the demand side can evaluate these IDs, expanding addressability.
- Reducing risk: With accurate metadata available in the EID field, demand-side partners can evaluate who is doing the match and make informed decisions on whether they want to act on that ID.
Next steps for the supply and demand-sides to consider
For supply-side and demand-side partners looking to utilize OpenRTB 2.6 to its full potential, here are some recommended steps:
For the supply-side:
- Follow IAB Specs and provide feedback: Ensure you understand and are following transparent practices. Ask questions on how to correctly implement the specifications.
- Vet identity partners: Choose partners who deliver the most trusted and accurate identifiers in the market.
- Be proactive: Have conversations with your partners to discuss how you plan to follow the latest specs, which identity partners you work with, and explain how you plan to provide additional signals to help buyers make better decisions.
We are beginning to see SSPs adopt this new protocol, including Sonobi and Yieldmo.
“The OpenRTB 2.6 specifications are a critical step forward in ensuring transparency and trust in programmatic advertising. By aligning with these standards, we empower our partners with the tools needed to navigate a cookieless future and drive measurable results.”
Michael Connolly, CEO, Sonobi
These additions to the OpenRTB protocol further imbue bidding transactions with transparency which will foster greater trust between partners. Moreover, the data now available is not only actionable, but auditable should a problem arise. Buyers can choose, or not, to trust an identifier based on the inserter, the provider and the method used to derive the ID. While debates within the IAB Tech Lab were spirited at times, they ultimately drove a collaborative process that shaped a solution designed to work effectively across the ecosystem.”
Mark McEachran, SVP of Product Management, Yieldmo
For the demand side:
- Evaluation: Use the EID metadata to assess all the IDs in the EID field, looking closely at the identity vendors’ reliability. Select partners who meet high standards of data clarity and accuracy.
- Collaboration: Establish open communication with supply-side partners and tech partners to ensure they follow the best practices in line with OpenRTB 2.6 guidelines and that there’s a shared understanding of the mutually agreed upon identifiers.
- Provide feedback: As OpenRTB 2.6 adoption grows, consistent feedback from demand-side partners will help the IAB refine these standards.
Moving forward with reliable data and data transparency
As the AdTech industry moves toward a cookieless reality, OpenRTB 2.6 signifies a substantial step toward a sustainable, transparent programmatic ecosystem. With proactive adoption by supply- and demand-side partners, the future of programmatic advertising will be driven by trust and transparency.
Experian, our partners, and our clients know the benefits of our Digital Graph and its support of both authenticated and inferred signals. We believe that if the supply-side abides by the OpenRTB 2.6 specifications and the demand-side uses and analyzes this data, the programmatic exchange will operate more fairly and deliver more reach.
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Supply-side platforms (SSPs) are expected to deliver more than inventory—they’re being asked to support sell-side targeting strategies, campaign results, and proof of performance. To meet that demand, SSPs need more than access to inventory. They need better data, better tools, and a way to bring it all together. Experian’s solutions for SSPs We built Experian’s solutions for SSPs with that demand in mind. By combining identity resolution, audience targeting, and third-party measurement, we help platforms move beyond basic transactions. Whether you’re doing sell-side targeting, supporting direct deals, or looking to support campaign validation, our tools make it easier to create value for buyers—and keep them coming back. Our solutions that help SSPs: Resolve identity across digital touchpoints using our industry-leading Digital Graph Build differentiated audiences using over 2,400 Experian Audiences and Partner Audiences in Audience Engine Support advertiser-direct relationships with tools to create, activate, and host custom segments Measure real outcomes like in-store visitation and sales through Outcomes, our third-party validated reporting suite Together, these capabilities allow SSPs to produce data-driven deals, increase addressability, and meet buyer demand for smarter, more measurable media. Campaign snapshot: Yieldmo + Experian Yieldmo, an advertising platform known for its creative formats and data-informed approach, has already put this solution to work. Here’s how they built a custom strategy for a major athletic retail client using Experian\’s joint solution for SSPs. The challenge: Drive in-store traffic and reach new buyers Yieldmo supports a leading athletic retailer’s seasonal campaigns focused on in-store traffic. This advertiser wanted to reach new buyers—specifically those who might otherwise shop with a competitor. To do this, they needed access to strong audience segments with reliable data and the flexibility to act quickly across channels. This was the first time Yieldmo applied Experian Audiences to this retailer’s campaigns. The stakes were high: the client was looking for better in-store outcomes and a more streamlined activation workflow. The solution: Experian\’s activation solution for SSPs Using Experian’s Audience Engine, which includes our proprietary and third-party data marketplace, Yieldmo built a flexible, high-performing media plan that spanned display inventory and included both conquesting and primary in-store shopper segments. The team selected and activated: Apparel and footwear audiences built from Experian and partner data providers In-store shopper segments targeting retail behavior signals Competitive purchasers to capture likely buyers from other athletic brands Our data marketplace allowed Yieldmo to combine Experian Audiences with Partner Audiences from providers like Alliant, Circana, Sports Innovation Lab, and Webbula—all in one place. Manual audience creation used to take days. Now, Yieldmo can build and activate campaigns through a streamlined, self-serve workflow. By working in the Audience Engine platform, Yieldmo was able to avoid multiple contracts and manual requests. They filtered audiences by brand, tailored segments to their goals, and launched without delays. “Experian’s data marketplace in Audience Engine fills a critical gap—letting us quickly search by brand, build smarter conquest segments, and activate custom audiences fast.”Abby Littlejohn, Director of Sales Planning, Yieldmo The results: Expected lift in store visits While final in-store lift results are pending, the early performance metrics are promising: Click-through rates are at and above historical benchmarks across both conquesting and primary shopper segments. Using Audience Engine’s self-serve tools, Yieldmo created audiences faster and more easily. They reduced their workload by minimizing the need for manual data wrangling. “We include Experian audience segments in 80% of formal RFPs. Between contract simplicity, data quality, and campaign results, Experian has become our go-to for third-party audience targeting.”Nelson Montouchet, AVP, Strategic Partnerships, Yieldmo Download the full case study Bring this to your platform Whether you’re looking to monetize more effectively, build deeper advertiser relationships, or stand out with sell-side targeting offerings, we designed Experian’s solutions for SSPs to do exactly that. With our industry-leading Digital Graph, over 2,400 syndicated audiences, partner data, flexible self-serve tools, and outcome-based measurement, SSPs can now move faster and go further—without compromising scale or precision. Get in touch with our team Latest posts

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Originally appeared in AdExchanger Google’s decision not to deprecate cookies in the Chrome browser after all caused a stir across the industry. Companies invested heavily in developing solutions aligned with the Privacy Sandbox as a survival tactic for the post-cookie landscape. At first glance, Google’s about-face may appear to undercut those efforts. It’s easy, and perhaps even satisfying for some – but inaccurate – to say “all that effort was for nothing.” Given Chrome’s dominance among browsers, AdTech companies had no choice but to prepare for “what if” scenarios. The same goes for cookie deprecation. Google’s plan to end support for third-party cookies would have removed a mechanism that has been a cornerstone of addressability for the past 15 years. To be clear, those efforts have not been wasted. They spurred innovation across the AdTech landscape, driving progress in privacy-first targeting, alternative identifiers, supply-path data activation, and real-time data enrichment – all of which will pay dividends for years to come. Whether born directly from Privacy Sandbox participation or inspired by the broader trend toward privacy reform, industry-wide preparation for cookie loss and browser disruption has yielded tangible benefits. Pressure from Google, Apple, and evolving regulations served as a catalyst for modernization that could shape the next decade of advertising technology. An industry anchored in product innovation AdTech is a fundamentally product-driven industry defined by short innovation cycles and the imperative to build and test rapidly. This DNA enables companies to stay resilient, evolve and deliver innovation. Change is good. Disruption can be even better – but only for those who embrace it. Google’s evolving stance on cookies and Privacy Sandbox doesn’t negate what’s been learned. If anything, it underscores the need to keep innovating. The next wave of disruption is likely right around the corner. The payoff While some may argue that the time and effort spent preparing for cookie loss was wasted, those efforts have functioned as a forcing mechanism for several innovations in data activation. Supply-side data activation and optimization, aka “curation,” is an alternative to the traditional approach to data activation. Unlike the traditional data management platform (DMP) to demand-side platform (DSP) activation flow, curation allows buyers to utilize supply-path data more directly. The upshot? Improved performance and pricing for media agencies and brand advertisers. As curation continues to evolve, it’s poised to play a central role in how advertisers and publishers transact. Real-time data enrichment is another area that has benefited from this period of accelerated innovation. Many companies were compelled to improve their tech stacks to align with Sandbox protocols. These updates, particularly in real-time data enrichment capabilities, are now laying the groundwork for future data activation strategies across both the buy and sell-sides. Exiting out of tunnel vision Over the past five years, the AdTech industry has invested deeply in planning for a future without cookies. Still those investments have been well worth it. While cookies are not going away, the broader deprecation of signal continues. The work that was done to prepare will inevitably inform the next evolution of our industry. Contact us Latest posts