If heading downtown for First Day/First Night, revelers are asked to be safe and enjoy themselves, with a constant refrain from officials of “If you see something, say something.”

Events begin around Copley — at Copley Square, Copley Place, the Prudential Center, the Boston Public Library, and the Old South Church — at noon. A program is available here.

“I want to urge everyone who’s watching to come out and celebrate First Night in the City of Boston,” Mayor Martin Walsh said at a press conference Wednesday. “Have fun, be safe, but also be smart when you come out and celebrate the ringing in of 2016.”

Walsh was joined by Boston Police Commissioner William Evans, Boston Fire Department Commissioner Joseph Finn, MBTA General Manager Frank DePaola, and Dusty Rhodes, President of Conventures Inc., which planned and produced the festivities.

This is the first time the event, which grows every year, is hosted by an independent group rather than the city. All events are free with no button system in place like last year, Rhodes said.

Also free is public transportation after 8 p.m., including the T and commuter rail. The T will run until 2 a.m. and the commuter rail until 1:30 a.m. Public transit is suggested in commuting to the square, especially as there are street closures.

Fireworks will be blasted off at two hours this evening: 7 p.m. at the Boston Common, and at midnight over Copley Square and the Boston Inner Harbor.

Officials ask that attendees not drink alcohol in the open at the festival and behave respectfully. They plan a colorful, safe, and music-filled celebration.

A heavy police presence will be deployed around the area, both visible and undercover. There is no specific and credible threat against the city, Evans said, but officers are prepared for any possible scenario.

Any violence is not usually concentrated around the family-friendly events during New Year’s, but rather in the outlying neighborhoods, Evans said.

“We don’t just deal with this night,” he said. “We have a plan for downtown, but we never lose sight that we have to keep an eye on the neighborhoods.”