Prebid Mobile SDK 3.0 delivers CPM gains while 4.0 roadmap targets publisher control

The Prebid project released details about its mobile SDK advancements during a webinar held on October 23, 2025. The session documented adoption metrics, technical improvements in SDK 3.0, and outlined the development roadmap for SDK 4.0 aimed at giving publishers greater control over in-app monetization.

Christian Janelli, Director of Product Management at Prebid, and Mike Mullin, Vice Chair of Prebid Mobile and Senior Product Manager at Index Exchange, hosted the session. Alex Fawcett from Relevant Digital, José Brandenstein from WetterOnline GmbH, and Alexander Savelyev from Verve also participated. The webinar covered technical achievements, implementation challenges, and strategic direction for the open-source header bidding technology.

Prebid Mobile now operates in more than 2,000 apps worldwide, with daily downloads increasing, according to the webinar. The SDK provides direct access to impression opportunities across apps, which helps reduce duplicated supply and enables cleaner auctions. The open-source development model has attracted participation from independent publishers and ad tech partners.

SDK 3.0 introduced plugin support allowing publishers to connect with bidders like Teads and InMobi, as well as identity or contextual data partners requiring on-device code. The version delivered improved rendering performance and better support for rewarded video and multi-format ad units across iOS and Android platforms.

On iOS, continued investment in SKAdNetwork and AdAttributionKit aims to capture more value from the growing gaming ad spend segment, according to the webinar materials. A new API lets publishers modify bid requests and attach additional data without requiring a full SDK update, providing agility for testing and optimization.

Several bug fixes and enhancements introduced in version 3.0 improved reliability in production environments, according to participants. SDK 4.0 development focuses on streamlining the developer experience through easier setup and configuration, expanding format support beyond display to include richer and video inventory, enhancing performance monitoring and latency tracking, and improving transparency and control for publishers over demand partner connections.

José Brandenstein from WetterOnline documented his team's implementation challenges. The main issues involved SDK compatibility with other tools, including Google's SDK, and ensuring seamless communication between app-side and server-side setups.

Brandenstein emphasized keeping SDKs fully updated and closely following Prebid's release notes, since updates often include critical fixes for features like GPID and SKAdNetwork support. Missing a version can result in broken implementations or inaccurate reporting, he noted.

After upgrading to SDK 3.0, WetterOnline activated GPID and SKAdNetwork integrations. Within two weeks, the team observed up to a 10% CPM uplift, confirming the value of consistent version maintenance and close coordination between ad ops, app developers, and SSP partners, according to Brandenstein.

He shared a troubleshooting insight: if reporting shows "unknown" GPID impressions, it usually means users haven't updated to the latest app version yet, not a technical issue.

Alex from Relevant Digital summarized four key best practices derived from WetterOnline's experience and broader publisher feedback during the webinar. Publishers should use OpenRTB fields for flexibility, as the newer SDK supports global and impression-level ORTB objects, making it easier to pass consistent data such as GPID and display manager info between web and app.

Publishers need to ensure OMID compliance by declaring open measurement parameters including partner name, version, and MRAID/OMID support to signal transparency and enable accurate viewability tracking. Before adding new bidders, publishers should confirm they've registered a Global Vendor ID to avoid compliance or performance issues in regions under GDPR or US privacy laws.

For iOS, implementing ATT signals remains important. Even if publishers choose not to track users, declaring App Tracking Transparency status helps maintain compliance and future-proofs the app against Apple's evolving privacy requirements, according to the webinar.

These practices make the Prebid Mobile SDK easier to maintain, more compliant, and better aligned with modern programmatic standards, according to the participants.

Alexander Savelyev from The Verve Group introduced the roadmap for Prebid Mobile SDK 4.0. The mission centers on giving mobile publishers more control, transparency, and flexibility over their monetization compared to closed mediation systems.

The roadmap includes three main focus areas. First, in-app bidding expansion aims to broaden adoption by making integration easier across different app types and ad stacks, including gaming. This includes developing new mediation adapters, simplifying codebases for iOS and Android, and enabling partners like Teads and InMobi to build directly on the SDK via open APIs.

Second, creative standardization will improve ad rendering consistency and measurement so that ads display and track correctly across formats, devices, and viewability vendors. The goal involves giving buyers greater confidence and predictability in Prebid-powered inventory.

Third, positioning Prebid Mobile as a platform involves modularizing the SDK, improving documentation, and expanding test coverage so developers can customize and extend it independently. The team aims to make Prebid SDK a developer-friendly, open platform that supports community-built extensions and automated testing.

SDK 4.0 continues the shift from a basic in-app bidding tool to a flexible, open ecosystem that bridges publishers, developers, and demand partners under a standardized, transparent framework, according to Savelyev.

The webinar included a question-and-answer session addressing technical implementation details. On tracking in-app banner impressions, the discussion noted three main methods currently in use: BURL in bid responses with the rendering SDK firing it when the ad appears, MRAID scripts within the creative to detect visibility, or OMID, the IAB Tech Lab's open measurement standard that now has over 95% market adoption.

The Prebid Mobile team is working to integrate OMID-based tracking directly into the SDK and Prebid Universal Creative, enabling automated impression firing once the visibility threshold is met. For now, publishers can continue using BURL or MRAID tracking until OMID support is fully released, according to the session materials.

On performance comparisons with other mediation platforms, the webinar clarified that Prebid SDK isn't meant to replace mediation platforms but to act as an additional demand source that can plug into existing mediation stacks. Performance depends on the publishers' connected bidders, SSPs, and DSPs. Unlike traditional mediation, Prebid takes no revenue cut, meaning publishers get paid directly by advertisers or bidders. Prebid operates as an open-source, community-driven project, so data and feedback must come from publishers and partners using it.

Regarding GAM Prebid rendered integration method, the session explained that Prebid Universal Creative and the Rendering API are two separate options. Publishers using PUC with an ad server such as GAM should continue using that setup, as it relies on Google's WebView for rendering. Those without an ad server, or looking to move away from one, can use the Prebid SDK's native rendering to display banners, videos, and native ads directly.

The SDK can also communicate with bidder plugins like Teads or InMobi, delegating rendering to them when needed. Publishers can either keep their current ad server workflow with PUC or adopt the SDK's built-in or plugin-based rendering for more flexibility, according to the webinar.

When asked about support for ad chains, such as Meta showing multiple ads at once to increase winning chances against mediation or performance campaigns, the webinar indicated Prebid remains open to bringing new ad formats like carousels into community discussions or GitHub issues. The goal involves standardizing innovative formats and moving them out of walled gardens into open programmatic environments.

On whether Teads can work with GAM in the classic integration, the session clarified that Teads can already serve demand through the standard Prebid Server integration. To access custom ad formats and advanced features offered by Teads, publishers need to use the Rendering API integration with the Teads plugin.

The Prebid Mobile developments occur as header bidding technology faces increased scrutiny over transaction ID handling and standards compliance. Prebid.org clarified its transaction ID policy on October 23, 2025, following months of industry debate.

The mobile advertising landscape continues adapting to new measurement standards. IAB Tech Lab integrated UniversalAdId into the Open Measurement SDK in June 2025, enabling consistent creative identification across platforms. Google integrated Open Measurement in its Mobile Ads SDKs in July 2021.

Google's AdMob platform announced major mediation updates in July 2025, adding bidding support from InMobi, ironSource, and Unity. The platform scheduled additional bidding releases for later in 2025 with Moloco and LINE.

Display & Video 360 stopped bidding on multiple waterfall calls for mobile apps in October 2024, transitioning to real-time bidding as the primary method for purchasing mobile app ad inventory. The shift occurred approximately one year after a similar transition in Google Ads.

The Trade Desk joined Prebid.org as a leader member in February 2020, with co-founder and Chief Technology Officer David Pickles joining the Board of Prebid.org. Google remains the only main player in RTB that is not a member of the header bidding organization.

The mobile SDK development roadmap reflects broader tensions in the programmatic advertising ecosystem between publisher control, buyer transparency, and technical standards compliance. The emphasis on open-source development and community-driven innovation contrasts with closed mediation platforms that take revenue cuts from publishers.

For publishers implementing in-app header bidding, the webinar documentation suggests prioritizing SDK updates, coordinating between technical and ad operations teams, ensuring compliance with privacy frameworks like ATT on iOS, and participating in the open-source community through feedback and testing.

The availability of plugin support and modular architecture in SDK 4.0 aims to reduce integration friction while maintaining transparency over demand connections. The focus on creative standardization addresses buyer concerns about measurement consistency that have historically limited investment in in-app inventory.

Timeline

• December 13, 2017 – Prebid.js 1.0 released with universal ad unit type support
• February 4, 2020 – The Trade Desk joins Prebid.org as leader member
• July 7, 2021 – Google integrates Open Measurement in Mobile Ads SDKs
• October 23, 2024 – DV360 transitions to real-time bidding for mobile apps
• June 15, 2025 – IAB Tech Lab integrates UniversalAdId into OM SDK version 1.5.5
• July 7, 2025 – Google launches major AdMob mediation updates with new bidding partners
• August 27, 2025 – IAB Tech Lab challenges Prebid transaction ID changes
• August 30, 2025 – Publishers drive Prebid transaction ID changes amid yield protection concerns
• October 23, 2025 – Prebid clarifies transaction ID policy after industry confusion
• October 23, 2025 – Prebid hosts webinar on Mobile SDK 3.0 achievements and 4.0 roadmap

Summary

Who: Prebid.org, Christian Janelli, Mike Mullin, Alex Fawcett, José Brandenstein, and Alexander Savelyev presented; WetterOnline GmbH served as case study; over 2,000 apps now implement the SDK

What: Prebid Mobile SDK 3.0 achievements documented including plugin support, improved rendering, SKAdNetwork investment, and flexible APIs; SDK 4.0 roadmap unveiled focusing on expanded in-app bidding, creative standardization, and platform modularization; WetterOnline reported up to 10% CPM uplift within two weeks of implementation

When: Webinar held on October 23, 2025; SDK 3.0 currently in production; SDK 4.0 development underway; WetterOnline observed results within two weeks of SDK 3.0 upgrade

Where: Global implementation across more than 2,000 apps; iOS and Android platforms; integration with mediation stacks including Google Ad Manager; open-source development through Prebid.org community

Why: To provide publishers direct access to impression opportunities, reduce duplicated supply, enable cleaner auctions, increase transparency, eliminate revenue cuts from closed mediation systems, and give publishers more control over monetization compared to closed platforms; SDK updates address compatibility, performance, privacy compliance, and developer experience improvements