Google is now allowing ad networks to bid for its AdSense publishers’ ad space. In an email sent to customers this week, Google outlines how publishers can now avail of the increased competition for their online advertising:

We're writing to let you know about an upcoming update in your AdSense account designed to help you generate the maximum revenue from your ad units. You'll soon be able to allow multiple ad networks to show on your pages, which means that advertisers from external Google-certified networks will be able to compete with AdWords advertisers for your ad space.

This is a significant move by Google. Yield optimisation is becoming a big growth area for non-premium display advertising. And Google wants to take full commercial advantage by allowing networks to bid for publishers’ ad space.

The long and mid tail remains a valuable source of inventory, and Google’s reach will make it an attractive prospect for ad networks. The increased completion could also result in higher CPM rates for publishers.

Google have clearly looked at what yield optimiser specialists have been offering publishers, and implemented similiar features into their new look Adsesne. Brand safety is a key USP for ad network optimisers, and Google stresses the importance of this in their announcement to publishers:

To ensure the quality of the ads appearing on your sites, we're certifying all participating ad networks for adherence to our standards for user privacy, ad quality and speed. You'll also have control over which networks can show ads on your pages - you can choose to opt out of receiving ads from specific networks, or all networks completely. This means you can continue to show ads from only AdWords advertisers if you like.

Publishers will be able to select and block ad networks from their Ad Review Centre. Although open to a small number of buyers initially, Google will look to add more networks in the coming months.

This could be part of a bigger exchange strategy for Google, as it looks to roll out the new and improved AdX exchange. The new AdX will look to sit Adsense and the DoubleClick exchange on the same platform, allowing agencies and ad networks the opportunity to buy across both.

This also appears to be a direct attempt to seize market share from the established yield optimisation players who optimise ad network relationships for long tail and mid tail publishers.