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, butt 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.
On Tuesday, a Microsoft spokesman said she couldn't provide additional information about the company's decision to support the HTTP header, instead referring Computerworld to Hachamovitch's Monday blog. Hachamovitch did not specifically explain Microsoft's reasoning in that post.
For its part, earlier this month Mozilla submitted its proposed Do Not Track HTTP Header to the Internet Engineering Task Force, another group that promotes Web standards. Mozilla jointly submitted its proposal with the Stanford team headed by Mayer.
Mozilla announced its Do Not Track support in late January, and added it to a beta of Firefox 4 several weeks later. Firefox 4 is slated to ship in final form later this month.
Firefox 4 has the HTTP header feature disabled by default. To turn it on, users must go to Preferences/Advanced, and check the "Tell web sites I do not want to be tracked" box. IE9 automatically switches on its Do Not Track HTTP header transmission as soon as the user subscribes to a Tracking Protection list.
Brookman said it was far from clear which Do Not Track technology would end up being adopted by advertisers and sites in the face of increased government pressure.
"This has sat dormant for three years, but since 2010, there's been a fury about [increased privacy]," he said. "Everyone is trying to figure this out. But I like the idea of Microsoft iterating ideas very quickly."
Because there are more questions than answers at the moment, Brookman hesitated to name a leader among the different browsers. "We don't have a scorecard yet," Brookman said of the in-flux situation.
Instead, the important thing is to keep privacy on the front burner.
"Let's get the critical support [Do Not Track] needs, enough ad networks to support it, a critical mass, and then work out what it means as we go along," Brookman said.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed. His e-mail address is email@example.com.