Google Inc. has bought Zagat, the popular restaurant recommendations and ratings authority, to expand its local content in the niche marketplace that includes Yelp and Yahoo Inc.

Google said the 32-year-old Zagat, which polls consumers and compiles reviews on restaurants around the world, will become a cornerstone of its "local offering" and work in tandem with its mapping services and core search engine.

Founded by Tim and Nina Zagat, their eponymous service provides pocket-sized guides to restaurants in more than 100 cities. It may be one of the earliest forms of user-generated content, Google Vice President Marissa Mayer said in a blogpost Thursday.

"We are thrilled to see our baby placed in such good hands and to start today as official 'Googlers,"' the founders said in a joint statement.

Zagat will go up against competing services popular with users on the Internet, including Yelp.