Walmart executives say that raising wages alone will not solve the problems many Americans have managing their cash flow. Rather, the company says, the new service is meant to help workers with the broader issues of financial management.

The app, called Even, has been used by other employers, but never on such a large scale as Walmart.

With the new service, every Walmart employee can obtain a portion of his or her earned wages eight times a year free of charge. For most of the workers, the so-called Instapays will be deducted from their next paycheck. The workers can pay extra if they want more than eight Instapays.

The Even app also helps workers manage their finances by pinpointing exactly how much they can safely spend before their next paycheck.

Alexis Adderley, who works nights in a Walmart distribution center in Fort Pierce, Fla., has started using the Even app as part of a pilot program.

At first she was suspicious, she said, that the app was yet another in a long line of financial products like payday advances and “overdraft protection” that end up driving low-income workers deeper into a hole.

But Ms. Adderley, the mother of boys ages 8, 7, 4 and 2, said she had been pleasantly surprised.

The app, which connects to her bank account, calculates how much she pays for housing, food and phone bills and tracks when she makes big monthly payments. With that data, Even provides Ms. Adderley a real-time estimate of how much she has to spend before payday.

She earns $19.25 an hour, more than the average Walmart employee, and works 30 hours a week. But money is still tight, especially since she was forced to leave her home after Hurricane Irma. Earlier this week, the app warned Ms. Adderley, 30, that she had only enough money to safely spend $9.08 before her next paycheck.