Google is to start serving advertisements to its users based on their browsing habits, the Web giant announced on Wednesday.
The company already offers advertising related to the site being surfed -- so long as that site is a Google AdSense partner or YouTube. But the beta test of what Google calls 'interest-based' advertising will take a wider view of the user's surfing habits to target served ads even more accurately. The service will launch on 8 April.
"These ads will associate categories of interest -- sport say, or gardening, cars, or pets -- with your browser, based on the types of sites you visit and the pages you view," Google's vice president of product management, Susan Wojcicki, wrote on the official Google blog. "We may then use those interest categories to show you more relevant text and display ads."
The new ad-serving system works by downloading a DoubleClick cookie to the user's browser to track their path through various AdSense-using sites. DoubleClick is an ad-serving company that was acquired by Google last year.
As with any other cookie, this tracking file can be cleared by the user at any time. By visiting Google's ad-preferences page, the user can opt out of having their surfing habits tracked, or input their own preferences for the subject matter of ads they would like to see.
As clearing the browser's cookies would effectively remove the opt-out cookie itself, however, Google has also released a plug-in for browsers that provides a permanent opt-out from the service.
Google is keen to stress the transparency of its approach. "We already clearly label most of the ads provided by Google on the AdSense partner network and on YouTube," Wojcicki wrote. "You can click on the labels to get more information about how we serve ads, and the information we use to show you ads. This year we will expand the range of ad formats and publishers that display labels that provide a way to learn more and make choices about Google's ad serving."
A spokesman for Google told CNET UK's sister site ZDNet UK on Wednesday morning that the company had "gone beyond the industry standard" for privacy in contextual advertising. "We were never going to be comfortable doing it unless we could offer this choice for the users," the spokesman said.
Asked whether there were any comparison to be made with Phorm, the ad-serving company that drew protests when it conducted user-monitoring trials with BT without first informing the subjects, the spokesman said Google had "been open and transparent from the start".