Open Bidding vs Header Bidding: Which Should Publishers Use?

Open Bidding (formerly Exchange Bidding/EBDA) is Google's server-to-server unified auction inside Ad Manager. Like header bidding, it lets third-party exchanges compete for your inventory in real time. Unlike header bidding, the auction happens on Google's servers, called directly from GAM.

The case for Open Bidding

• Zero page latency: no extra JavaScript runs in the browser.
• One bill, one report: revenue from all participating exchanges flows through your GAM payment.
• Simple setup: enable partners in the GAM UI, no wrapper code.

The case for header bidding

• Better match rates: client-side auctions see the user's browser context, so buyers can identify and value users more accurately, which usually means higher CPMs.
• More demand: many strong bidders participate in Prebid but not in Open Bidding.
• Transparency and control: you own the auction logic, the data and the timeout strategy. Open Bidding charges exchanges a fee that effectively comes out of your yield, and reporting granularity is limited.

Real-world performance

Across publishers we manage, client-side Prebid typically wins 55–70% of the impressions where both stacks compete, precisely because of richer user signals. But Open Bidding still adds 8–15% incremental revenue on impressions Prebid partners undervalue — particularly in geos where client-side match rates are weak.

The right answer: run both, referee with data

The two are not mutually exclusive — they compete in the same GAM unified auction. The professional setup is Prebid client-side for your premium bidders, Prebid Server or Open Bidding for the long tail, AdX as the anchor demand, and AI-driven floors keeping every channel honest. Then measure incrementality per partner per channel and prune what doesn't pay its way. That referee role — continuous, data-driven demand curation — is exactly what PubMonetX automates.