In May 2005, Google unveiled AdSense for feeds, a version of AdSense than runs on RSS and Atom feeds that have more than 100 active subscribers. According to the Google Blog, "advertisers have their ads placed in the most appropriate feed articles; publishers are paid for their original content; readers see relevant advertising — and in the long run, more quality feeds to choose from".
AdSense for feeds works by inserting images into a feed. When the image is displayed by the reader/browser, Google writes the ad content into the image that it returns. The ad content is chosen based on the content of the feed surrounding the image. When the user clicks the image, he or she is redirected to the advertiser's site in the same way as regular AdSense ads.