What about credit cards? Debit cards?

Debit cards are just a handy way to write an electronic check. The money you use when you use a debit card is the money in your checking account, so it’s already included in M1.
Credit cards, however, are NOT MONEY. Credit cards are really handy way to electronically take out a loan from the bank. Using a credit card doesn’t really pay for a purchase. It just delays the date when the payment will be made (and adds some interest charges to it). Credit cards are NOT considered part of M1.

Debit cards are just a handy way to write an electronic check. The money you use when you use a debit card is the money in your checking account, so it’s already included in M1.