Money transfer apps, which allow you to quickly pay friends and family through your smartphone, have grown in popularity in recent years. And the coronavirus pandemic has only expanded their use — to pay gig workers, make donations or simply avoid using cash.

The apps have even been promoted as a way to receive government stimulus checks.

But linking the mobile apps to your credit cards may get more expensive, thanks to a payment industry change.

To use an app for cash transfers, customers typically connect it to an outside payment source. Most users link their debit card or a bank account, since in most cases that lets them transfer money without charge. A few apps, however, also give customers the option to link to a credit card and pay a small fee (about 3 percent) for “peer to peer” payments, like splitting the dinner tab. Those apps include PayPal and its Venmo arm, as well as Cash App, which is owned by Square. (Zelle, the app backed by traditional banks, doesn’t accept credit cards.)

But there has been a change in the way the money transfers are coded as they zip from your phone and move through the Visa and Mastercard payment networks. That change enables banks to also charge their own, separate cash advance fees — typically $10 but sometimes much more — for payments made using credit cards on those networks. The fees don’t apply when customers make a purchase.