Whenever Caroline Keane opens the Venmo app, she always intends to just go in and out. But, inevitably, she gets sucked into the mobile money-transfer service — specifically, its social feed, where she can see friends and co-workers requesting cash from one another for drinks, dinners and Ubers. Scrolling through the app gives the 23-year-old PR professional a particular sense of anxiety: Is everyone hanging out without her?

“Seeing these transactions — even among people I have no desire to be hanging out with — creates a sense of emptiness and unease,” Keane told The Post. “It’s like, ‘S–t, everybody is doing something on Thursday night, and I’m sitting and reading my book. Am I a loser?’ ”

Since its 2012 launch, Venmo has become a big part of city life, especially for millennials. Colleagues use it to split bills at restaurants and for cab rides; roommates use it to divvy up the cost of cleaning supplies. Essentially, one person pays the tab and then requests a Venmo payment from their accompanying pals. In the past 12 months, users have sent more than a combined $40 billion through the app. A 2017 Fast Company article reported more than 7 million active monthly users — up from 3,000 in 2012.

Unlike other payment apps, such as Cash or Zelle, Venmo has a social component: a public feed where you can see all your connections’ transactions. (Venmo does allow users to make their activity private, but many don’t, because it’s a complicated process.) The real-time stream is a barrage of silly emojis, impenetrable inside jokes and invoices detailing fabulous weekends in the Hamptons and at hot nightclubs. And, according to some users, it’s ruining their lives.

“I do see Venmo anxiety with younger people,” said Melanie Greenberg, a Bay Area clinical psychologist and author of “The Stress-Proof Brain.”

“I think it’s part of a larger phenomenon of pressure that’s on young people to fit in and to always be having a fun time,” she said. “When you see that everyone . . . was at a party and you weren’t invited, you can feel left out.”

Monique Lewis, a 38-year-old who works in marketing, admits to feeling “sort of unwanted” when she sees friends Venmoing one another. It’s even meant the end of some relationships.

“I’ll ask [friends], ‘I noticed you and such-and-such went here — why wasn’t I included?’ ” said the Upper West Sider. “I can tell when people are sincere in their response, or they’re beating around the bush and making up excuses . . . It definitely makes me reassess our friendship.”

Union Square resident Lindsey Metselaar, who runs a social-media management company and hosts a dating podcast called “We Met at Acme,” said she uses the app to keep tabs on the people she dates.

“I’ll see if they have any recent activity and … if it matches up with what they had told me they were doing that night,” said the 27-year-old.

Randall Bellows, a photographer based in Williamsburg, however, would rather not learn how his love interests are spending their time and money.

In March, the 31-year-old opened the app one day to retrieve a payment and saw that his ex-girlfriend had Venmoed her new squeeze for a “ring re-size.”

“That’s how I found out she was engaged,” Bellows told The Post. “I mean, I’m happy she found someone, but to find that out on Venmo — I was like, ‘Really?’ … It was a surreal experience.”