Bill de Blasio is inviting everyone to his swearing in ceremony on the steps of City Hall and throwing a massive after-party at Gracie Mansion.

The mayor-elect has decided to open his swearing ceremony to the general public on Jan. 1 and will throwing a bash at his new home a few days later.

De Blasio and his wife, Chirlane McCray, will host the soiree in their new digs as the Upper East Side institution will be occupied for the first time in 12 years.

Mayor Bloomberg threw a fancy party on his own dime – but didn’t invite the public — for his first two inaugurations but skipped the festivities the third time around.