Google has agreed to build support for Do Not Track into Chrome so its Web browser can tell Web sites when people don't want advertisers scrutinizing their behavior.

The Do Not Track technology modifies communications between browsers and servers so people can signal that they don't want their browsing behavior to become the basis for ad targeting.

Mozilla developed Do Not Track and built it into its Firefox Web browser. Microsoft followed suit not long after with Internet Explorer, Apple has enabled it as an option for developers in Safari 5.1, and Opera is building it into the forthcoming Opera 12.

Now Google's getting on board, too, with Chrome.

"We plan to implement Do Not Track across our browser and advertising systems by the end of the year," a Google representative said today in a statement.

Why not earlier? Do Not Track wasn't mature enough an idea for Google, apparently:

We have always thought the idea of DNT was interesting, but there didn't seem to be a wide consensus on what "tracking" really means. We didn't feel it was responsible to allow users to send a header in Chrome that largely had no effect and no agreed-upon meaning. Going forward, the scope is now clear, and we know that the header will be respected by the industry.

Do Not Track has been somewhat academic because it requires cooperation from Web sites to respect the feature. But Google, Microsoft, Yahoo, AOL, and other Internet powers just pledged to support Do Not Track on their sites, making the feature much more important.

"We're pleased to join a broad industry agreement to respect the 'Do Not Track' header in a consistent and meaningful way that offers users choice and clearly explained browser controls," Susan Wojcicki, Google's senior vice president of advertising, said in a statement.

The Do Not Track news is emerging in conjunction with the Obama administration's proposed Consumer Privacy Bill of Rights being unveiled later today.

The Wall Street Journal first reported the Chrome support for Do Not Track. The Journal also said Apple will make Do Not Track a standard feature in the Mac OS X 10.8 Mountain Lion operating system due to arrive this summer.

For the impatient, there's also the Do Not Track Plus browser extension that works with Chrome, IE, Firefox, and Safari. It will support Opera at a later date.

Updated at 2:12 a.m. PT to add that Opera is supporting Do Not Track in its browser, too.