Prebid Launches Publisher-Controlled Universal Identifier

SharedID Links Epsilon’s PubCommon ID with’s ID; Bringing Coverage of Third-Party ID and Persistence of First Party IDs in a Standardized, Community-Owned Format

Gains Support from Diverse Online Community Including Adform, Business Insider, NewsCorp, MediaMath and Zeta

NEW YORK--() today announced the general availability of a community-owned, open source identifier that includes both first- and third-party components. SharedID links Epsilon’s industry-leading, first-party PubCommon ID with the third-party ID to provide a more complete identity solution suite for programmatic advertising.

With the eventual demise of third-party cookies, the advertising industry is pursuing a variety of methods for targeting and attribution, including obtaining user consent via log-in or single-sign on solutions. SharedID is designed to complement those solutions by addressing users who choose to not log-in, or publishers who choose to not transmit those log-ins to buyers. SharedID is a publisher controlled solution that writes a first-party value via the Prebid wrapper, and can be used either to transmit first-party information to buyers or to create audience segments within the publisher domain – and allow for those segments to be shared across hundreds of publishers.

Building on’s commitment to ensuring open, transparent transactions across the industry, SharedID embraces the open source and community-driven approach that allows the open internet and ad tech at large to embrace a common, transparent namespace. SharedID also has a single-point opt-out to give consumers full control over their privacy and their advertising preferences. SharedID, which includes PubCommon ID, establishes a common ID that publishers, exchanges, and buyers all use, increasing ID consistency.

“The fact that is standardizing on PubCommon ID to bring the industry’s first community-driven approach to identity is validation of the hard work we put into building the industry-leading technology,” said Chad Peplinski, Chief Media Officer at Epsilon. “When we launched it, we wanted to remove ownership disputes and business risk from the identity debate. We succeeded in that goal, and thousands of publishers have adopted PubCommon ID since its launch. Now, as we transfer ownership of the technology, we are confident that Prebid’s SharedID will scale and be adopted by even more publishers.”

Epsilon launched PubCommon ID in 2018 to offer publishers an open-source, first-party cookie solution that generates unique user IDs from a publisher’s domain and links those IDs to the publisher’s first-party data. The unique user ID can be utilized to improve user matching, especially for iOS and MacOS browsers, and is compatible with ever-changing browser regulations. It is lightweight, self-contained and does not impact latency. Publishers that have adopted PubCommon ID have seen a 23% increase in revenue and 30% increase in filled impressions.

“The advertising industry is welcoming in a new era of consumer privacy and control – led by the publisher community,” said Tom Kershaw, Chairperson of and CTO of Magnite. “SharedID gives publishers control over how identifiers are written into their pages and apps, and who gets to receive them. It also will allow us to address the whole of the internet – including those users who choose not to log in.”

SharedID launches with support from leading publishers, exchanges and DSPs including: Insider Inc., News Corp., CafeMedia, Publishers Clearing House, Magnite, Adform, MediaMath, and Zeta.

“Merging PubCommon ID and SharedID under Prebid now is great news and also perfect timing for us,” added Jakob Bak, CTO at Adform. “We recently went live with 1st-party based programmatic trading on our platform, so we have been facing the challenge of onboarding of publishers at scale to especially PubCommon ID. This news will certainly increase the speed of adoption which has already been going well with advertisers and publishers eager to re-engage Safari users and prepare for future Chrome changes.”

“The release of SharedID represents a significant step toward unified identity across the open Web and the enabling of a value exchange with publishers and consumer privacy at the foci,” said Anudit Vikram, SVP Product, MediaMath. “Bringing enhanced scale, accuracy, and control; this shared identifier will allow the ecosystem to become ready for the seismic shift that a cookieless world will bring to digital advertising.”

“Given Marketers require cross-publisher IDs to measure and improve the effectiveness of their advertising across the open web, Zeta fully supports the Prebid’s goals to bring an privacy-by-design pseudonymous ID to improve people’s digital experiences,” added Joshua Koran, Head of Zeta Innovation Labs, Zeta Global. “Important to the scaled adoption of this open source solution is that it does not preference any marketplace participant, while simultaneously improving the auditability of marketplace transactions to better protect people’s important privacy rights as well as reducing the discrepancies caused by existing ID syncing solutions.”

Stephanie Layser, VP, Advertising Technology, News Corp. commented: "In a post-third-party cookie world, publishers will be uniquely positioned to control the flow of data into the ad tech ecosystem. Aligning on a trusted, transparent identity solution that includes a unified opt-out is essential. Prebid's initiative is the first step the industry needs to take as it embarks on rearchitecting the advertising ecosystem as a fairer market for participants and a safer environment for consumers."

How SharedID Works

By leveraging the existing global identifier footprint of Prebid members, SharedID launches as a scaled, readily available identity solution. Via the Prebid User ID Module publishers can write the SharedID common identifier as either a first-party or third-party value. Prebid gives publishers complete autonomous control over SharedID and all IDs written to their pages.

With SharedID, cookie syncing becomes unnecessary as every party in the ecosystem will utilize the same shared identifier. As more and more companies deprecate proprietary IDs, the industry will be freed from the reliance on hundreds of cookies, greatly reducing the overall identifier footprint for the entire industry while moving to an open source publisher-controlled first-party model. is an industry-wide initiative supported by a diverse group of exchanges, publishers, DSPs, and third-party developers dedicated to promoting fair, transparent, and efficient open-source header bidding solutions. Members of the Prebid publisher tier include: AdvanceLocal, Ascendeum, CPEX, CafeMedia, Chegg, DiDNA, Freestar, GlewedTV, Hive Media Group, Insider, Inc., MediaVine, NewsCorp., OCM, Publisher’s Clearing House, Pubwise, SheMedia and Sortable. CafeMedia is the board representative of the publisher tier.


Formed in September of 2017, is an independent organization designed to ensure and promote fair, transparent, and efficient header bidding across the industry. Funded by dues-paying members, it manages the open source projects Prebid.js, Prebid Mobile, Prebid Server, Prebid Video, Prebid Native, and others. is open to all companies who are part of the programmatic ecosystem, from ad tech vendors to publishers and others. We believe that, working together, we can drive standardized, transparent technology for advertising that will make it easier for buyers and sellers to transact at scale in a fully programmatic ecosystem.

About Epsilon

Epsilon is the leader in outcome-based marketing. We enable marketing that’s built on proof, not promises. Through Epsilon PeopleCloud, the marketing platform for personalizing consumer journeys with performance transparency, Epsilon helps marketers anticipate, activate and prove measurable business outcomes. Powered by CORE ID®, the most accurate and stable identity management platform representing 200+ million people, Epsilon’s award-winning data and technology is rooted in privacy by design and underpinned by powerful AI. With more than 50 years of experience in personalization and performance working with the world’s top brands, agencies and publishers, Epsilon is a trusted partner leading CRM, digital media, loyalty and email programs. Positioned at the core of Publicis Groupe, Epsilon is a global company with over 8,000 employees in over 40 offices around the world. For more information, visit Follow us on Twitter at @EpsilonMktg.


Media Contacts
Charlstie Veith

Membership Contact


Media Contacts
Charlstie Veith

Membership Contact