Google has rewritten its link unit matching system for AdSense. Link units in AdSense ads display a list of topics that are relevant to the content of the publisher’s page. When a user clicks a topic, Google shows a page of related ads. AdSense publishers can earn from valid user clicks on the ads on this resulting page.

"Many publishers have found that link units offer monetization similar to that of ad units and provide a more integrated user experience," says Jerry Krikheli, Engineering Manager for Link Units.

"The new system is much smarter: it not only uses more sophisticated topic ranking algorithms but also continuously optimizes by learning which topics have the most appeal to the visitors of your site," explains Krikheli. "The results are overwhelmingly positive — topic quality, user response rate to topics and ads, and monetization metrics have all improved in significant, measurable ways."

Google says link units are effective because they’re targeted to the interests of users. "Because users directly interact with the ad unit, they’re more likely to be interested in the ads they eventually see," the company says.

Do you use link unit ads?