Specific User StreamY Combinator startup MixPanel debuted a new, free analytics tool today called User Streams that allows web publishers to track individuals browsing their site in real-time and group similar users into clusters.

The User Streams tool will be free to everyone and will complement MixPanel’s premium real-time analytics services that help companies understand how users interact with web applications.

With most real-time analytics tools you get information about tens of thousands of users all interacting with a web site at the same time, but you don’t have an understanding of what was common that made something successful, MixPanel cofounder Suhail Doshi told VentureBeat. User Streams differs from competitors like Chartbeat and Reinvigorate because it can analyze data on a micro level, he said.

While the tool can be useful for anyone wishing to gather data on specific user behavior, it’ll be particularly useful for user interface and user experience designers.

Individuals are identified using IP addresses or information from third-party services and automatically tags each person with aliases like “Crimson Alpha”,  “Maroon Beta”, etc. to make it easier to digest. However, publishers can change a stream’s name to whatever they like. That data is stored for a 45-day period and only uses information that’s publicly displayed or made available with consent of the user.

Founded in 2009, MixPanel has raised a total of $1.75 million to build its analytics services. The startup, which has customers that include Quora, Bebo, Slide and Posterous, tracks data for 2,000 sites, according to Doshi.

Check out some additional screenshots of the User Streams tool below.

Specific User Stream

StreamsStream Users