Google's (NASDAQ: GOOG) YouTube has announced a new analytics tool that will enable publishers and advertisers to track viewership on the popular video-sharing site.

Freely available to anyone with a YouTube account, the Insight feature offers detailed information about who is watching their videos, such as statistics on viewers by geographic region.

Insight builds on the rudimentary tracking tools YouTube had previously offered users, such as comments, viewer ratings and the popularity of a clip relative to all other content on the site. But with the new offering, the runaway leader in online video has taken a great leap forward in becoming an engine for ad revenue.

"Insight gives the creators an inside look into the viewing trends of their videos on YouTube, and helps them to increase views and become more popular," YouTube product manager Tracy Chan wrote in Google's company blog.

YouTube partners will be able to track the lifespan of their videos, comparing the popularity of their own content with similar offerings over a certain period of time.

Advertisers will be able to apply the metrics to evaluating and planning their campaigns, tapping into the wisdom of what Chan described as "one of the world's largest focus groups." Getting a bead on the demographic and chronological nuances of an ad campaign that reaches an audience the size of YouTube's could be a great boon for advertisers.

"Advertisers are always looking for metrics that help them determine the ROI of their campaigns. YouTube Insight provides advertisers with information that helps them better understand their audience -- who they are, where they come from, what they watch, and when," a YouTube spokeswoman told InternetNews.com. "As a result, they can better tailor their marketing efforts to run more targeted campaigns on YouTube to reach the right viewers."

In January, YouTube served up one-third of the 9.8 billion videos Americans watched online, according to online tracking firm comScore (NASDAQ: SCOR).

The announcement makes good on Google's recent promises to "turn up the dial" on monetizing YouTube, which it purchased for $1.65 billion in October 2006.

Advertising on YouTube uses Google's InVideo format, which places a banner at the bottom of the video player that expands when a user clicks on it. Google recently extended InVideo to its AdSense platform for placing ads on third-party Web sites.

Earlier this month, YouTube opened a set of APIs for developers to add videos from its library to their own sites, in the process extending the reach of its advertisers.

YouTube said it would add new features to Insight fairly quickly, such as the ability to keep track of the referring sites that direct traffic to certain videos.

Scanning the comments in response to the YouTube blog post announcing Insight, the reaction is mixed. Several users welcomed the new feature, but many of them reiterated their dismay over YouTube dropping its sorting features, where users could view content ranked by rating or total views.

Asked about the users' reaction, the YouTube spokeswoman said simply that "We have a very vocal community, and we are constantly changing and updating features on our site based on their feedback."