CoStar Group, Inc. is a leading global provider of commercial and residential real estate information, analytics, and online marketplaces. Headquartered in Arlington, Virginia, the company operates a portfolio of prominent brands including CoStar, Apartments.com, LoopNet, Homes.com, and STR. CoStar is distinctive for its massive proprietary database of real estate data and its dominant position in digitizing property discovery and research for brokers, investors, and consumers.