As more and more consumers turn to the web for free streams of their favorite television shows, marketers in turn want more precise data about who exactly is watching.

NBC is the first network to break down that door, offering advertisers streaming numbers and demographic information for shows like "The Office" and "Heroes," similar to the data available for television viewers. The data will be available through Nielsen Online's VideoCensus system starting next month, according to MarketWatch.

Previously, NBC offered demographic information for NBC.com as a whole, but it didn't break the data down by specific show.

The move is the first step in NBC's more ambitious goal to offer advertisers a complete breakdown of audiences who watch original TV broadcasts, web streams, and digitally recorded video. NBC will initially offer information only from NBC.com, and not Hulu, the property it co-owns with News Corp.