At most banks the ability to overdraw when you swipe your debit card is allowed on an opt-in basis. At many banks the default option is to allow the customer to overdraw with their debit card. At most banks the language around being allowed to overdraw in your account contract is intentionally confusing. You can usually change this selection online or in you bank app, but if you're confused call the help line on the back of your card. I don't advise going in to a branch, as the branch bankers are the ones with the incentive to get your money, the call centers actually don't care as much since the credit goes to the branches performance metrics.

At ALL banks certain payments will always be able to overdraw your account REGARDLESS of your opt-in/out selection. These are recurring payments for things like gym memberships or Netflix, paper checks, and many other forms of ACH payment.

An important note: this specifically affects checking/savings accounts and their DEBIT cards. CREDIT cards are different.

Source: Used to work in a bank branch and had to work my ass off every time I opened an account to ensure that people were aware of how and when they could overdraw bc banks want to steal your money and that's not cool.