Scribd is a digital library, featuring an ebook, audiobook and comic book subscription service that includes New York Times Best-Sellers and classics. Launched in 2007 by Trip Adler and Jared Friedman, and headquartered in San Francisco, CA, Scribd also features written works contributed by users around the world. Backed by Y Combinator, Charles River Ventures, and Redpoint Ventures, Scribd serves more than 80 million active readers coming to the site every month. Scribd’s subscription service is available on Android, iOS, and Windows Phone smartphones and tablets, as well as the Kindle Fire, Nook, and personal computers for a fee which lets readers have unlimited access to more than 500,000 books from over 900 publishers, including Harper Collins, Simon and Schuster, RosettaBooks, and Workman. In November 2014, audiobooks were added and in February 2015 comic books were added, both without an additional fee to the subscription.