Facebook’s mobile ad network is looking to sell more ads on a broader number of websites, diversifying beyond the game and utility apps that dominate its client base. Some of its new targets for mobile ad sales are large publishers such as USA Today and Hearst, which have started selling ads through Facebook Audience Network after plugging into the social network’s fast-loading article-hosting platform, Instant Articles.

For the next part of that strategy, Audience Network is testing a new type of technology called “header bidding,” which many of those publishers like because they believe it will boost competition for their ad space. Until recently, publishers selling ads through computerized marketplaces decided which ad exchanges to use based on what the exchanges paid for ad space previously. That meant publishers didn't always get the best price. Header bidding changes that by allowing exchanges to compete directly against each other for space. Publishers use pieces of code from ad exchanges to immediately alert them when ad space is available.