It's a good time to love a mosh pit, if Austin City Limits Music Fest 2019 is any indication. And they're not just in places where you'd expect to find them.

Fans of everyone from Billie Eilish to Lil Uzi Vert got in the pit and thrashed about. Mosh pits were also present at performances from rappers 21 Savage, Denzel Curry and Duckwrth and teenage rockers Laundry Day. Even people at the Silent Disco got in on the moshing, despite a strict no-moshing policy. (A DJ late Sunday night of Weekend Two even had to cut the music briefly to remind the crowd it was a no-no.)

To the uninitiated, mosh pits can seem angry or violent — like a place where one might get hurt. But, as those willing to chance some lumps and stomped-on toes can attest, there's an etiquette to the pit. Inside the pit at ACL Fest, the experience often proved communal and therapeutic, with slam-dancing fans holding each other up and even stopping the action to retrieve dropped phones and wallets for others.

Take Idles. (Please! I'd argue their live show is hands down one of the most life-affirming music experiences a human being can have in 2019.) Their ultra-inclusive but visceral punk rock offers the perfect metaphor of the pit experience: intimidating on the outside, sweet on the inside. During the band’s Sunday afternoon set at ACL Fest, the pit formed like clouds twisting into a hurricane, pulling people into the vortex. At other times, the pit opened up and sweat-soaked fans took turns dancing solo in the center.

Frontman Joe Talbot policed the Idles pit early on to ensure everyone was on their best behavior, giving a good summary of pit etiquette in the process.

"Hey, muscle men in the pit,” Talbot said. “Please watch the people around you and look out for your neighbors. Or (expletive) off."

Ashley Millhousen of Nashville got in the pit at Idles and Denzel Curry where “the entire crowd opened up.” Of the pit at Idles, she said, "Everyone was so united. It seems so angry, but everyone was so friendly."

Then there’s taking things up a level, crowd surfing. Sunday afternoon marked Millhousen’s first time getting up. She said the experience was incredible. "I will 100% do it again," she said.

Osmar Alanis of McAllen is a lover of punk music and a veteran of the pit. He was at ACL Fest on Sunday for Idles. Osmar said he got into the pit more in the past, but not so much now that he’s older.

“But I made an exception last weekend for Idles," Osmar said.

Last weekend at Idles' late-night ACL Fest show at the Mohawk, Osmar's friend Eric Vasqez was pulled on stage to drum with the band. It was one of those heart-warming moments of a fan's day being made — made even better by the fact that Vasquez killed it.