Before founding first round, he was a founder of Half.com, a fixed price marketplace connecting buyers and sellers of used books, movies, and music products.

[2] In 1992, during his sophomore year at the Wharton School, Kopelman co-founded Infonautics, based in Wayne, Pennsylvania.

He is an investor, director, and advisor to OnDeck Capital, Flatiron Health, Aster Data Systems, Knewton, Gigya, AltSchool, The Black Tux, Five Below, Massdrop, Like.com, IronPort, Mint.com, Monetate, LinkedIn, ModCloth, AppNexus, BankSimple, Swipely, True & Co., Wanelo, Warby Parker, Ring.com, Numerai, OpenX, LiveOps, Boxed.com, Clover Health, Upstart and Discourse.

[1] In 2001, he and his wife created the Kopelman Foundation, a non-profit philanthropic organization to provide start-up grants to social entrepreneurs.

[22] In 2002, the Kopelman Foundation funded a project to digitize and host the complete text of the Jewish Encyclopedia online.