The term "scaled back" is all relative, because Barack Obama's 60th birthday bash was still a bash, with what appeared to be several hundred party revelers on hand to celebrate.

There were tons of celebs who showed ... including Steven Spielberg, Tom Hanks, George Clooney, Jay-Z, Beyonce, Bradley Cooper, Don Cheadle, Gabrielle Union, Dwyane Wade, Erykah Badu, Steven Colbert, Bruce Springsteen and more.

The former Prez hit the dance floor under the massive tent ... without a mask. As you know, the CDC, Dr. Fauci and many other experts have urged people to wear masks inside because of the Delta variant, and it's already drawing criticism.

The party looked super fun ... but the plan to keep things under wraps crashed and burned early on, as Erykah Badu and others posted photos and videos of the event.

Napkins of the event were embossed with the numbers, 44x60 ... the 44, obviously, refers to his presidency, and the 60 is obvious.

Partygoers even took shots of the bathroom, with a lint roller, Advil and antiperspirant ... frankly the sign of a good party.

The food and drinks looked pretty amazing ... lots of the food was vegetarian, but there was reportedly an oyster bar which is requisite fare for a Martha's Vineyard soiree.

Obama hit the dance floor for quite some time, dressed casually as he made the rounds.

Alicia Keys and John Legend both sang Happy Birthday to 44.

The party snarled traffic around the island, at when it started winding down at 1 AM Sunday, one officer was overheard calling traffic a "s*** show."