Kopelman is best known as the founder of Half.com, a fixed price marketplace connecting buyers and sellers of used books, movies and music products. In 2000, Kopelman sold Half.com to EBay for US $350 million.
Kopelman was born in Great Neck, New York. He attended the Wharton School at the University of Pennsylvania. In 1992, during his sophomore year, Josh co-founded Infonautics Corporation – an Internet information company. In 1996, Infonautics went public on the NASDAQ stock exchange. Kopelman left Infonautics in 1999 to found Half.com.
After selling Half.com to eBay, Kopelman remained with eBay for three years.
In 2001 Josh and his wife created the Kopelman Foundation, a non-profit organization focused on angel philanthropy to provide “start-up” grants to social entrepreneurs. In 2002 the Kopelman Foundation funded a project to digitize and host the complete text of the Jewish Encyclopedia online.
In 2005, together with Adnan Aziz and Jay Minkoff, Kopelman founded First Flavor, a taste marketing company. He is now on the board of directors for First Flavor.
Current work 
Kopelman is currently Managing Director of First Round Capital, a seed-stage venture fund. He is an investor, director and advisor to a variety of businesses, most in the software and Internet domain, including Jingle Networks, Odeo, Eventful, Krugle, Ambient Devices, del.icio.us, IronPort, RockYou!, myYearbook, Knewton, VideoEgg, Wikia and several other firms.
While Kopelman has invested in a large number of Web 2.0 companies, Kopelman warned that too many Web 2.0 entrepreneurs are targeting an audience of 53,651  people, the number of then-current subscribers to TechCrunch, a popular weblog that covers the internet industry. In 2007, Kopelman helped to coin the phrase the Implicit Web to better describe the Semantic Web.
- Redeye VC - Josh Kopelman's Blog
- Josh Kopelman's public profile with his positions and investments
- First Round Capital
- First Round Capital management page including a brief biography of Kopelman
- The Kopelman Foundation
- Midas Capital Kopelman's private investment fund, which preceded First Round Capital
- Video interview with Josh Kopelman on the 10th anniversary of Half.com