Abstract: Methods, systems, and apparatus include computer programs encoded on a computer-readable storage medium for providing content. A method includes: identifying a placement opportunity for content for a user device characterized as being included in a group in which the group is defined by a user having a specific attribute; providing a bid request to content sponsors, the bid request including characteristic information that identifies information known to a serving system about the user without specifying the attribute that is associated with the user; receiving conditional bids conditioned on the user having a specific attribute from the content sponsors that establish a price to be used in an auction for the placement opportunity; evaluating the received bids in view of the attribute associated with the user including using received bids in the auction to determine a content item for the placement opportunity; and providing a content item for the placement opportunity.

Abstract: Methods, systems, and apparatus include computer programs encoded on a computer-readable storage medium for providing content. A method includes: identifying a placement opportunity for content for a user device characterized as being included in a group in which the group is defined by a user having a specific attribute; providing a bid request to content sponsors, the bid request including characteristic information that identifies information known to a serving system about the user without specifying the attribute that is associated with the user; receiving conditional bids conditioned on the user having a specific attribute from the content sponsors that establish a price to be used in an auction for the placement opportunity; evaluating the received bids in view of the attribute associated with the user including using received bids in the auction to determine a content item for the placement opportunity; and providing a content item for the placement opportunity.