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Foursquare is principally funded by Union Square Ventures , Andreessen Horowitz , O'Reilly AlphaTech Ventures , and Spark Capital . The company raised $ million in its Series A round and $20 million in its Series B round .   On June 24, 2011, Foursquare raised $50 million on a $600 million valuation.  Their Series D round funding of $41 million was announced on April 11, 2013 and led by Silver Lake Partners .  Unlike prior funding rounds that had been financed via equity , a good portion of Series D came in the form of convertible debt from existing investors.