A typical service, Ciamacco says, opens with a band that would fit in at the Coachella festival, were it not for the Jesus lyrics: “What a savior, my Redeemer/Friend of sinners, one like me.” (In one podcast, a pastor, sermonizing about society’s obsession with markers of achievement, uses an Internet-approved term of endearment to channel his audience, asking, “When am I going to get my own bae?”)

At the end, a member of the “worship team” will call on parishioners to tithe and pass the collection plate. But not all people reach into their wallet. Many take out their phone instead.

Ciamacco gives each week, using the Tithe.ly app. It takes fewer than five taps, and built-in geolocation means he can contribute at any of the 1,000 churches that subscribe—a feature that’s especially useful around holidays like Easter, when many people travel.

Tithe.ly lets worshipers set up automatic recurring payments, but because Ciamacco’s paycheck fluctuates with his work as a freelance video producer, he tithes on demand—usually about 10 percent of whatever he’s brought in.

“We see people giving all times of day and night”

Although churches are saying a collective hallelujah that a new generation of devotees is filling pews, a youthful congregation has its limitations. Twentysomethings might find religion, but not a lot of them have found that six-figure job. They don’t carry cash—and what, exactly, is a personal check? Still, about a quarter of them use mobile payment apps such as PayPal and Venmo regularly, according to a recent Accenture survey.

And enormously popular services such as Seamless, Uber, and Amazon.com have normalized one-tap payments—91 percent of millennials use their phone to buy something at least once a month, market-research firm Statista says.

Tithe.ly is one of a handful of apps leveraging that spending behavior for the good of the church. Pushpay, which about 3,000 congregations employ, works similarly; worshipers decide whether to donate to a general budget or a specific program the institution designates. Another, EasyTithe, features a text-to-give option. It also provides technology for a Square-like credit card reader to await the faithful in church lobbies. Regardless of which app a congregation chooses, the point is convenience.

“We call it frictionless giving,” says Dean Sweetman, Tithe.ly’s co-founder and a former minister at C3 Atlanta. He designed the app with C3’s wallet-light clientele in mind: “We see people giving all times of day and night. Nothing stands in the way.”

Apparently not. Churches using tithing apps report they see more donations, more often, from more people. (Subscribing establishments either pay a monthly fee or allow the app to collect a cut of each gift. Tithe.ly lets donators cover this; Pushpay promises churches a 5 percent spike in donations or their money back.) But getting parishes with pastors and members older than 40 to sign on has been more Job-like.

Tradition is hard to overcome. “In some churches, if you let the plate go by and you don’t put something in, you feel a little guilty,” says Brad Hill, who works in platform services at EasyTithe. To combat that, some congregations print out cards that say, “I gave online.”

Ciamacco’s friend James Crocker, also 25, says it’s much more awkward to donate the old way: “Putting your personal credit card details on a piece of paper and leaving it there? For millennials, there’s no way.” Ciamacco agrees, if for different reasons. “I was so anti writing my name on an envelope—it was a holier-than-thou thing,” he says. “When Tithe.ly came out, I was like, ‘Hell, yeah.’ ”