Matvei Michkov tied it 1-1 on a breakaway at 1:56 of the second period after skating into a lead pass from Sean Couturier in the neutral zone and scoring on a snap shot over Allen's glove.
Couturier stole a pass attempt by Devils defenseman Luke Hughes along the Flyers blue line before springing Michkov, who leads NHL rookies with 14 goals.
"I'm kind of reading his eyes and, at that point, me and [Joel Farabee] had to switch since he was down low and I had the D-man," Couturier said. "I was kind of in between and just ready to step up on him. [Luke Hughes] fanned on his pass so once I got it, I knew [Michkov] was gone, so I laid it there like an alley-oop and let him do his thing."
Ersson denied a wrist shot from the slot by Dawson Mercer on a New Jersey power play at 17:19 to keep the game tied.
"[Ersson] has steadied himself," Philadelphia coach John Tortorella said. "He didn't get a lot of action tonight and we ate shots all over the place, but he looks confident, and I hope it continues."