Google is building profiles of customers’ browsing habits so it can target them with advertisements.
The search engine is tracking the websites people visit to build up a database of their interests.
Launching the system on Google’s blog, vice-president of Google product management Susan Wojcicki, said, "Our advertisers and publisher partners have been asking us for a long time to offer interest-based advertising."
The service is running as a beta test on Google’s partner sites and 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," Wojcicki said. "We may then use those interest categories to show you more relevant text and display ads."
She said Google might "infer" an interest in a topic from the websites one might visit. "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," she said.
But Google users will also be able to edit the profiles Google builds based on the website categories they visit. They will also have the choice of opting out of the service.
Commenting on the launch, Cambridge University professor and privacy activist Richard Clayton, said, "Google is not doing anything different today, compared with what it was doing on Monday."
He said he would prefer that Google allowed users to opt-in rather than opt-out.