They work together, play ping pong together and meet at the same coffee shops to brainstorm on what will make the next great Internet start-up.

Welcome to the heart of New York City’s Silicon Alley. Many of the city’s web designers, software engineers and start-up founders work out of a stretch along Broadway and Fifth Avenue, between Union Square and Madison Square Park.

A new report out last week showed that New York is giving the West Coast’s Silicon Valley a run for its money, emerging a national leader in cranking out web start-ups.

Calling the city “the nation’s second-leading hub for technology companies,” the Center for an Urban Future report shows that New York is dwarfing other cities in its rapidly multiplying start-up sector.

According to the report, the number of information technology jobs in New York has increased 28.7 percent in the last five years, from 41,100 to 52,900.

The report estimates there have been 1,000 start-ups created here in that same time, with many of them hunkered within a few blocks of each other. About 40 start-ups, from Shelby.tv to Tumblr, have offices between and around Union Square and the Flatiron district.

Jonathan Bowles, director of the Center for an Urban Future, which released the report, said eight different companies are located at 902 Broadway alone, between 20th and 21st streets.

“That address is right smack in the middle of the area where we are seeing the greatest concentration of start-up activity – between Union Square and Flatiron,” he said.

Because their offices are located so close together, employees have coffee meetings at the same cafes — Grey Dog is a favorite — and see each while in line for lunch at Shake Shack.

“We all kind of cluster together,” said Reece Pacheco, 29, founder and CEO of Shelby.tv, a video-sharing site with offices located at 23rd Street and Park Avenue. “I’m just constantly running into people when I’m going out for lunch.”

Choosing to be near each other

Pacheco said he intentionally wanted Shelby.tv to be headquartered near other tech start-ups.

“I think there’s a natural tendency to want to be in the same area and make it easier to get to meetings and make it easier to meet up with friends at other companies,” he told Metro.

While searching for office space, they looked south of 23rd Street, he said.

“We want to be 23rd and below,” he said. “We want to be near places where we have coffee meetings.”

This leads to a lot of run-ins with other techies. “Shake Shack is a staple of the New York tech community for sure,” he said.

In his building, five other start-ups also operate — and those are just the ones where he knows people, he said.

Their office includes a ping pong table, drum set and guitars – and a shower, which is helpful for Pacheco, who lives at the office for now, because he travels so much he doesn’t have an apartment.

Jeff Levinson, at Enterproid, which created the app Divide that lets users swap in and out of work and personal profiles on one phone, wanted to be around other start-ups – and their building at 22nd Street between Fifth and Sixth Avenues had good history, he said.

Google bought the start-up that previously operated in their office space.

“The space has that good buy-out karma,” he said.