Downtown Manhattan paradegoers are swapping bathroom tips, tricks and even the entry codes to coveted restrooms near City Hall as an estimated one million revelers packed the streets for hours on Thursday.

“It was rough,” said John Rodriguez of Delaware, who told The Post he held it in for an hour and a half before finding a Starbucks with a public restroom.

“We need more public bathrooms and more businesses to open their doors and accommodate,” Rodriguez, 37, said.

“I came prepared not to use the bathroom,” said attendee Patricia, who refused to drink anything during the morning of the historic parade.

Yet another paradegoer, who declined to share his name, desperately waited for hours before finding relief at Nancy Whiskey pub on Broadway.

“I have to pee so bad, man,” he curtly told a reporter before scurrying off to the bathroom.

The city urged fans to “plan ahead” in an Instagram post Wednesday, advising there would be “no dedicated bathroom access!”

But that hasn’t stopped fans – many of whom have already been partying in the Canyon of Heroes for hours – from swapping advice, including the code for a Think Coffee location on 13th Street.

“Don’t drink water or coffee that morning,” one fan encouraged in a New York Knicks fans Facebook group.

“Get there early to get a spot guys,” yet another fan said, “and don’t drink too much! Businesses don’t let you go to the bathroom down there.

“It’s going to be gross,” they added, “because everyone will pee in the street.”

At least a few fans, including 20-year-old Samuel Butler of the Bronx, brazenly found relief in a Manhattan street – as a cop parked nearby reportedly shrugged off the desperate attempt.

“I found a secluded alleyway. There were other guys there, too,” Butler said, laughing. “You do what you have to do and just leave.  You have got to go when you have to go.  

“There was a cop near the alleyway, but he didn’t care.” 

— Additional reporting by Steven Vago, Georgett Roberts and Brandon Cruz