Eli5: When your credit card doesn’t read at a credit card machine, why does covering it with a plastic bag suddenly make it work?

Question

Had this done multiple time at the register. Card not reading, so the cashier will cover the ribbon or the chip with a plastic bag and YATZEE, it goes through. Why?

In: 407

Answer 1

Overtime, some of the magnetized bits on the stripe get what’s called ‘smeared’ out of position. Basically your card gets sloppy. When you swipe the card the reader also reads the smeared parts which present as additional or corrupted signals. When you wrap your card in a bag it creates distance between your card and the reader so the reader isn’t able to read those few bits that have smeared out of position because they present a much weaker signal.