Consumer Federation of California

Instead of using tiny trackers that dozens of companies attach to websites to monitor people’s browsing, Google is considering a switch to a system that would create its own anonymous identifier for each individual, a Google official said Wednesday.

Such a move, in the early stages of consideration by the search giant, would shake up the $120 billion online-advertising industry, which relies on the ubiquitous “cookies” to target and deliver advertising.

“We believe that technological enhancements can improve users’ security while ensuring the Web remains economically viable. We and others have a number of concepts in this area, but they’re all at very early stages,” said a Google spokeswoman.

The proposal could force advertisers to turn to Google, already the biggest player in online advertising, to get information about people’s shopping habits and preferences—rather than tracking users themselves.

“It’s going to limit what advertisers can find out about people,” said Nanda Kishore, chief technology officer for Share This, a firm that places cookies on websites. “Essentially the data about users will be in the hands of just a few companies.”

Mike Anderson, chief technology officer of Tealium, a software company that helps advertisers track users, said advertisers might be willing to trade in cookies for an identifier because it could help them create more detailed portraits of consumers. Right now, advertisers may place cookies on websites, but each uses different code, so they can’t tell whether they’re tracking the same user.

Google’s proposal, which was reported earlier by USA Today, could give the advertisers ability to track people more widely. “The Internet gets a lot cleaner at that point,” Mr. Anderson said.

In the debate over online privacy, cookies have been under attack. Some consumers are nervous about tracking, and don’t like that cookies can see what they are doing or pass their information to third parties, enabling firms to develop increasingly detailed profiles of consumer behavior.

This year, Mozilla announced plans to launch an automatic cookie blocking feature on its Firefox browser. Microsoft Corp. launched a default “Do Not Track” feature on its latest Internet Explorer browser. Apple Inc.’s Safari browser has blocked cookies since 2003. Google has resisted efforts to block cookies on its Chrome browser.

Jonathan Mayer, a Stanford University professor who studies online advertising and privacy, said it was unclear that so-called anonymous codes would actually protect privacy. “Instead of reinventing the wheel, why not start by supporting the consumer control technology that’s already in every major web browser?” he said.