This is a list of startup tech companies that went through the YC program and have physical offices in San Francisco.
Y Combinator is an accelerator and Venture Capital investment firm that provides funding for startups. Twice a year they invest a small amount of money in a large number of startups. These are known as the spring and winter batches. At the end of a batch there is a highly publicized demo day where Venture Capitalists watch and invest in the companies further. Y Combinator was founded by Paul Graham, Jessica Livingston, Trevor Blackwell and Robert Tappan Morris. The Y Combinator investment firm and startup accelerator is a driving force in the Silicon Valley tech and startup ecosystem.