Open Auction
A public programmatic auction where any qualified advertiser can bid on available ad inventory.
What is an Open Auction?
An open auction (also called an open marketplace or open exchange) is a programmatic transaction method where publisher ad inventory is made available to all qualified advertisers and DSPs connected to the ad exchange. Any advertiser meeting the basic eligibility requirements can bid on impressions, creating maximum competition but with less publisher control over who appears on their site.
Open auctions are the most common form of programmatic trading, accounting for the majority of programmatic display transactions. They operate through real-time bidding (RTB), where each impression is auctioned individually in milliseconds. The highest bid wins, subject to the publisher's floor price and any advertiser quality filters.
Why It Matters for Publishers
Open auctions are typically the starting point for publisher monetization and remain the foundation of most ad revenue. They provide the broadest possible demand pool and the highest fill rates because any advertiser can participate. For publishers without the traffic or relationships to negotiate direct deals or PMPs, open auctions provide immediate access to millions of advertisers worldwide.
However, open auction CPMs are generally lower than PMP or programmatic direct pricing because advertisers don't receive the exclusivity or premium guarantees those channels offer. The open auction should be viewed as the revenue floor — the baseline that other programmatic strategies build upon.
Tips for Optimization
- Use floor prices strategically: Set floor prices to prevent your inventory from being sold too cheaply. Start conservatively and lower floors if fill rate drops significantly.
- Maximize demand sources: The more SSPs and exchanges connected to your open auction through header bidding, the more competition there is for each impression.
- Implement dynamic floor pricing: Use tools that automatically adjust floor prices based on time of day, geography, ad size, and historical bid data to maximize yield.
- Layer with PMP and direct: Structure your ad stack so that programmatic direct and PMP deals get priority, with open auction as the fallback. This ensures you capture premium pricing when available while maintaining high fill rates through the open auction.