Google will add support for "Do Not Track" to its Chrome browser by the end of this year.
The move is a reversal for Google, which has resisted supporting the technology that lets users opt out of the online tracking conducted by websites and advertisers.
Google's change of heart came as the White House today pushed a privacy bill of rights and said it would introduce new online privacy legislation in Congress.
Chrome joins other browsers -- Microsoft's Internet Explorer 9 (IE9) and Mozilla's Firefox -- which can already transmit special information with every HTTP page request that tells sites the user does not want to be tracked.
Apple's Safari currently supports Do Not Track, although turning it on requires a user to select "Send Do Not Track HTTP Header" from the "Developer" menu on the browser; Apple will make the setting easier to find in the Privacy section of Safari's Preferences pane this summer when it releases OS X Mountain Lion.
Opera, from the Norwegian browser maker Opera Software, does not support Do Not Track. Two weeks ago, however, Opera launched an experimental build of its desktop browser with support for for the anti-tracking technology.
"This is a great step forward," said Jonathan Mayer, a graduate student in computer science and law at Stanford University. Mayer is one of two principal researchers at Stanford who have been working on the Do Not Track technology that uses information in the HTTP header to universally opt out of all online tracking. "For some time, Google has been the last holdout among the major browsers."
Mayer called out "mad kudos" to the advertising industry for getting behind Do Not Track, but said only part of the problem has been settled.
"As a technology model, Do Not Track is clearly superior to an opt-out mechanism," said Mayer, referring to commitments by Google and other members of the Digital Advertising Alliance (DAA) to support the technology on their websites. "So the technology question is now settled: It's Do Not Track."
What's not settled, Mayer pointed out, is what Do Not Track means to the companies and websites that will acknowledge the user's call not to be followed. "The [Do Not Track] header has two parts. One is the technology, but the other is what it means to those that support it, what companies will have to do on their end," said Mayer.
"On the technology side, this is an unambiguous win, but on the policy side there is still a lot of work to be done," he said.
According to Mayer, DAA members have not actually agreed to not track users, but to not serve them targeted ads using the data accumulated by tracking cookies, the Web mechanism that can follow users' movements from one site to another.
Safari on OS X Mountain Lion, slated for shipping this summer, includes a privacy preference option to switch on Do Not Track.
He and others noted the difference.
"Big advertisers in the DAA [have committed] to responding to the Do Not Track header," said Alex Fowler, the global privacy and public policy leader at Mozilla, in a Thursday blog post . "What that response will be is still unclear, and we have some ongoing concerns to resolve."
Mozilla was the first browser maker to add Do Not Track support to its software.
Both Mayer and Fowler noted that work will continue in the W3C (World Wide Web Consortium) to create an industry-wide standard for the policies Do Not Track should cover.
"The ad industry side will try to say that the policy part of Do Not Track is done, and that we can all go home now," said Mayer. "Privacy advocates will say, 'No, the DAA does not go far enough.' So there's lots of work still to be done."
The silver lining of today's announcement is that Chrome's adoption of Do Not Track puts the option in front of a majority of Internet users: According to Web metrics company Net Applications, the browsers that now, or will later this year, support the header request accounted for 98% of those used last month.
"This is absolutely a great step in the right direction," said Mayer.
Google did not immediately reply to questions about the time line of Chrome's support for Do Not Track, or how the browser will present the option to users.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer , on Google+ or subscribe to Gregg's RSS feed . His email address is email@example.com .
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