1. A method comprising: receiving, by one or more computers, a reference image; receiving, by the one or more computers, a bid associated with the reference image, the bid comprising a bid for presenting a sponsored-content item, storing, by the one or more computers, the received bid in association with the reference image and the sponsored-content item; and receiving a request for an advertisement, the request including a bid image; in response to the request for the advertisement, using image or object recognition techniques to compare the reference image to the bid image to determine a match confidence level; comparing the match confidence level to a threshold; and presenting the sponsored-content item based on the a determination that the match confidence level exceeds the threshold.