If the format sounds familiar, it is no accident. But Mr. Shapiro’s bet with Fans.com is that other social networks are ill-suited as platforms to express the effusive passions people have for music, sports and other kinds of entertainment.

“There is no platform for being a fan,” he said. “Facebook was meant to be a connector to friends and family. But if you are a Slayer fan, you might not want to post about that, if you work at Chase Bank or if your grandma is on your Facebook page.”

For more than two years, Mr. Shapiro has been quietly developing Fans.com with a team of 10, including Seth Schiesel, a former reporter and critic for The New York Times who, like Mr. Shapiro, is a die-hard jam-band fan. (Mr. Schiesel said that Mr. Shapiro first told him of his idea before a Phish show at Madison Square Garden on Dec. 29, 2011.)

The site’s core is a database of five million concerts going back decades. Users can tag individual shows they have attended, and post media and links to a feed connected to each artist or event. The site will make its public debut on Thursday with live video feeds from Lockn’, Mr. Shapiro’s four-day festival in Arrington, Va., featuring Phish, My Morning Jacket and Phil Lesh of the Grateful Dead.

For now, Fans.com is a rudimentary database of concert listings. But Mr. Shapiro wants to expand it into sports and other areas. He also views it as a potential marketing tool that can be used by artists and promoters to target their most engaged listeners by tracking the data that users submit about how many concerts they have attended and where.