Google starts tracking users for better ads

Google will start looking at browsing history in order to display more relevant advertising, the web search giant announced today, raising privacy concerns.

Previously, displayed ads were based on what users put into Google's search engine, as well as the content of a page. "There are some situations, however, where a keyword or the content of a web page simply doesn't give us enough information to serve highly relevant ads," Susan Wojcicki, vice president of product management, said in a blog post.

Now, Google is trialling a beta of what it has dubbed "interest-based advertising" on partner sites as well as Google's own YouTube. "These ads will associate categories of interest say sports, gardening, cars, pets with your browser, based on the types of sites you visit and the pages you view," said Wojcicki. "We may then use those interest categories to show you more relevant text and display ads."

"Interest-based advertising also helps advertisers tailor ads for you based on your previous interactions with them, such as visits to their websites," she added. "So if you visit an online sports store, you may later be shown ads on other websites offering you a discount on running shoes during that store's upcoming sale."

Google will let users set their own favoured categories, or set which topics they'd rather not see.

Google admitted there are privacy concerns, saying it's tackling the issue in three ways, by clearly labelling adverts, by letting users say which categories they don't want to see ads for, and by allowing opting out of the AdSense advertising cookie. To ensure that last choice, Google has developed a plug-in that keeps users opted out.

The system has already been run by data watchdog the Information Commissioner's Office, which said in a statement: "We are pleased that the preference manager feature allows users a high level of control over how their information is used and that the method by which users can choose to opt out is saved permanently."

Other privacy groups weren't convinced. Simon Davies, head of Privacy International, told the BBC: "Yet again Google has developed and launched a major initiative without any consultation with its users. And yet again Google will walk into a privacy minefield."

Google has recently come under fire from the Liberal Democrats over its Latitude mobile tracking system.