The road to establish an industry standard for Do Not Track has been long and winding.

Last year, efforts at consensus stalled, grinding the work of the World Wide Web Consortium’s Tracking Protection Working Group to a halt.

But after more than three years, co-chair Justin Brookman announced that the Working Group finally agreed to a definition of “Do Not Track.” Specifically, the group set a “tracking preference expression” that defines “the DNT request header field as an HTTP mechanism for expressing the user’s preference regarding tracking, an HTML DOM property to make that expression readable by scripts, and APIs that allow scripts to register site-specific exceptions granted by the user.”

In other words, consumers can request that ad networks not collect their information, although certain types of data may still be collected (though the extent of such data is yet to be determined). The Working Group noted that the specification doesn’t define the requirements for complying with a user’s expressed tracking preference and that a compliance regime remains a work in progress.

In a blog post, Brookman wrote that reaching the agreement and creating a standardized meaning of the oft-debated term “is a big deal.” He encouraged readers to review and provide feedback on the proposal. Comments will be accepted until June 18.

In other tracking news, the Digital Advertising Alliance unveiled a new data tracking option for consumers that would allow them to opt out of data collection by clicking the blue icon that appears on ads. Two years in the making, “browser choice” is expected to be released in the coming weeks.

The opt-out will still allow ad networks some collection of data. “For the Internet to function, there still has to be some data collection,” Stu Ingis, counsel for the DAA, told AdWeek. “We’ll have the whole industry buying into it,” DAA executive director Lou Mastria told the publication. “The broad buy-in is what makes it a meaningful program. We won’t face the challenge about implementation and enforcement.”

To read the Working Group’s tracking preference expression, click here.

Why it matters: Brookman touted the technical specification as “a huge milestone” in his blog post, but the advertising industry believes “browser choice” has a better chance at success because of the industry’s ability to provide compliance and maintain enforcement. The W3C’s definition “may be a technical step, but it falls short as a privacy step,” Mastria told AdWeek. “That’s the challenge. The W3C doesn’t deliver a privacy regime that works. Consumers can send the signal, but so what.”