Since Jan. 1, Boston residents who rent out their homes through websites like Airbnb and HomeAway have been required to register with the city — per its new short-term rental ordinance.

But more than 90 days after the ordinance went into effect, not many short-term rentals have been registered.

The city says it has received more than 150 applications for short-term rentals. That’s a far cry from the number of Airbnb rentals in the city alone, which the company estimated at 6,300 back in November.

The registry is critical to the city’s short-term rental ordinance. It's supposed to help the city get a handle on the growing short-term rental market. Companies that host illegal listings are required to take them down, and they face a $300-per-night fine for each illegal listing. (Those who rent out units that are not registered with the city face fines too.)

The requirement of booking sites is currently held up in federal court due to a lawsuit filed by Airbnb. The city argues that Airbnb facilitates illegal listings. But Airbnb says hosts are responsible for their listings, and the ordinance would force the company to monitor and remove third-party content.

To comply with the ordinance, Airbnb and other companies would need to cross reference listings with the city’s registry. But “the registry wouldn't tell you much right now,” city attorney Adam Cederbaum told Judge Leo Sorokin during a hearing in the lawsuit Monday.

“To be frank, there has not been wide adoption of our registry yet,” Cederbaum said.

It's possible some residents are holding off on registration because of the ongoing Airbnb lawsuit. The city says it plans to do more community outreach to let residents know they need to register if they plan to rent out their homes.

It's worth noting that a new state law will create a statewide registry for short-term rentals when it goes into effect July 1.