“It’s pretty astonishing,” said Gabby Warshawer, director of research at CityRealty, a research firm. “Clearly there’s a lot of supply right now. We’re seeing longer lease terms, which is fairly new. And months of free rent.”

Free rent is hardly what you would expect in Brooklyn, where demand for housing has been rising for a decade, driven by the borough’s reputation as a haven of youth, hipness and do-it-yourself entrepreneurialism. But the original hip neighborhood, Williamsburg, is now expensive. And with the pending temporary shutdown of the L subway line in 2019 lengthening the commute into Manhattan, that neighborhood is no longer as appealing.

The boom in this corner of Brooklyn, which has one of the biggest transit centers in the city, owes a lot to the city’s 2004 rezoning of the downtown area to encourage the development of office towers and some residential buildings that could compete with Jersey City for back office operations. At first, there was little activity because the city was offering tenants and developers enormous subsidies to rebuild and move to Lower Manhattan after the Sept. 11 terrorist attacks. But the creation of an arts district around the Brooklyn Academy of Music and the Barclays arena at Flatbush and Atlantic Avenues, and the adjoining Atlantic Yards development, now known as Pacific Park, inspired interest in the area. And the city’s population has swelled, to an estimated 8.6 million people a year ago from 8.2 million people in 2010, setting off a seemingly unquenchable thirst for housing, especially given job growth in Brooklyn, which outpaces the city over all.

Developers and consultants are not predicting that rents will plunge, but they do expect them to stagnate and perhaps ease in the short term.