Microsoft yesterday followed Mozilla's lead by adding support to IE9 for the same "Do Not Track" technology used by Firefox 4.
The feature, dubbed "Do Not Track User Preference" by Microsoft, is another way to let users opt out of the online tracking conducted by Web sites and advertisers. Firefox 4 -- and now IE9 -- will transmit special information with every HTTP page request, telling the site that the user does not want to be tracked.
IE9 already had a different technology in place. Called "Tracking Protection," it relies on published lists to selectively block third-party sites and content embedded in Web sites.
Microsoft quietly added Do Not Track User Preference -- Mozilla calls it "Do Not Track HTTP Header" -- to IE9 between the browser's February's release candidate build and Monday's final edition.
Privacy experts applauded Microsoft's move.
"The two technologies are complementary," said Justin Brookman, the director of consumer privacy at the Center for Democracy & Technology (CDT). "There's no clash between the two, and I like the idea of them working in tandem."
"Major props to the IE team," said Jonathan Mayer, a graduate student in computer science and law at Stanford University, in a Twitter message Tuesday. Mayer is one of two principal researchers at Stanford working on a Do Not Track technology that uses information in the HTTP header to universally opt out of all online tracking.
Microsoft still considers Tracking Protection as IE9's primary tool for online tracking privacy, but hinted it added HTTP header support to cover the bases. "We will continue to provide features well beyond the minimum standards to keep consumers in control of their safety and privacy," Dean Hachamovitch, the Microsoft executive who heads IE's engineering efforts, said on a company blog late Monday.
Tracking Protection and the HTTP header work very differently. The former uses lists published by other organizations to actively block ad-tracking content. The latter, however, relies on sites and advertisers that track users to modify code on their end to respond to the Do Not Track request.
Microsoft's decision to add support for the HTTP header didn't come as a surprise, said Brookman, who pointed out the Redmond, Wash. developer inserted the feature in a February proposal to the W3C (World Wide Web Consortium), the primary standards body for the Web.