Since we announced the Trusted Server initiative at our Signal Shift event in March, one of the questions that has come up repeatedly in conversations with publishers and ad tech companies is, “Doesn’t Prebid Server already do all of this?”
The short answer to this question is no. Let’s delve deeper and explain why both software frameworks provide value to publishers, working in tandem to offer robust, privacy-first monetization capabilities under greater publisher control.
We’ll start by explaining what each technology is designed to do.
What is the Trusted Server?
The Trusted Server is a publisher-controlled, edge cloud middleware that acts as an intelligent ad router orchestrating between direct sold and programmatic sales, as well as any interaction with the publisher’s ad server and content, empowering publishers with unprecedented control.
Its primary function is to enable the capture and packaging of client-side signals—normally collected by third parties via code like JavaScript and stored in browser local storage—to support publisher monetization within a server-side framework that publishers fully control.
Key Functions of Trusted Server:
- Signal Collection & Identity Packaging: Collects on-page signals (e.g., context, user behavior, consent signals) and packages them to enable publisher third parties to provision their services in a server-side architecture that is not dependent on current or future browser restrictions.
- Maintains Publisher Monetization Operations: Operates under the publisher’s first-party domain, rewrites third-party ad tech calls to first-party calls to maintain advertising utility, and manages ad-related data securely at the edge for performance.
- Flexible Integration: Works with or without tags and doesn’t require client-side scripting, enabling tagless or server-side implementations.
- Enables Third-Party Services: Provides scalable mechanisms for consent management platforms (CMPs), identity providers, measurement vendors, fraud detection, and other ad tech components to operate safely under publisher governance.
- Not an Auction Server: Trusted Server does not conduct auctions. It simply receives auction results (e.g., from Prebid Server or another SSP) and reconciles them with the publisher’s ad server against direct-sold prioritization.
- DOM Integration: Stitches final ad responses, direct sold or programmatic, into the page DOM, preserving user experience and site performance.
What is Prebid Server?
Prebid Server, on the other hand, is a server-side auction engine built and maintained by the Prebid community. Its role is to run header bidding auctions, collecting bids from demand sources and returning the winning ad creative.
Key Functions of Prebid Server:
- Runs Auctions: Collects bid requests from demand partners, scores bids, and selects winners.
- Demand Integration: Interfaces with SSPs, DSPs, and other demand sources.
- Impression Context Only: Operates primarily with impression-level information, often relying on client-side scripts or signals passed into the auction request.
- Limited Page-Level Context: Unlike Trusted Server, Prebid Server does not have complete visibility into the broader context of the page or ongoing user interactions at the page level.
Better together
Rather than viewing Trusted Server and Prebid Server as competing open-source frameworks, it’s more accurate to think of them as complementary components of a modern, privacy-forward ad stack.
Here’s how they work together in the Request part of the process:
- Signal Collection (Trusted Server): When a user visits a page, the Trusted Server collects all relevant signals, including contextual data, consent strings, synthetic IDs, and other relevant signals.
- Identity & Privacy Handling: Trusted Server packages this data in a privacy-safe manner under the publisher’s control and sends it to Prebid Server to run the auction using the packaged identity and context data provided by Trusted Server.
And here is the Response part of the process, where the Trusted Server ingests the auction results from Prebid Server.
- Ad Delivery (Trusted Server): Once an ad is selected, Trusted Server stitches the creative into the DOM, ensuring compliance and user experience standards are maintained.
The table below provides more detail on the specific activities that comprise each round-trip request and response, illustrating how Trusted Server builds upon what Prebid Server offers to create a more comprehensive solution for Publisher monetization.
| Capability | Trusted Server | Prebid Server |
|---|---|---|
| Auction execution responsibility |  |  |
| Auction results interpretation responsibility | | |
| Ad creative stitching (HTML/JS rewrites) | | |
| Publisher DevOps Control (less AdOps dependent) | | |
| Request level edge storage (stored requests, cache) | |  |
| Modular Logic Control (not static exec of pre-config adapters) | | |
| Works with Prebid.js |  | |
| Works without Prebid.js | | |
| Modular 3rd-party integrations (identity, brand safety) | | |
| Bidder adapter direct integrations | | |
| OpenRTB bidstream control and communication | | |
| Client-side signal packaging and manipulation | | |
| Runs under publisher’s domain (1st-party only calls) |  | |
| Ability to rewrite and modify content and header responses | | |
| Ad Request routing based on rule sets (e.g., direct sold, RTB, etc.) | | |
| SSID & CMP injection and syncing into the bidstream | | |
| Ability to set server-side HTTP cookies and global synthetic IDs | | |
| Fraud detection / IVT filtering support | | |
| Orchestration of complete page logic with full context & user session | | |
As this table illustrates, the simplest way to distinguish between Trusted Server and Prebid Server is to focus on their roles within a bid request and response transaction. Trusted Server is the publisher-controlled signal and rendering layer, while Prebid Server remains the core auction engine. Together, they offer publishers a robust, modular, and privacy-compliant way to manage advertising in the post-cookie era.
If you’re interested in learning more about Trusted Server or getting involved, we encourage you to visit the Trusted Server page or contact us directly. We’re always looking for new perspectives and contributions to help shape the future of digital advertising.
Jason Evans
Trusted Server Technical Architect
IAB Tech Lab Consultant