Despite their common use, credit card generators are not intrinsically bad. In fact, credit card companies themselves use them to come up with numbers to issue on their cards. The software tells the computer to come up with a string of numbers of a certain length, and to apply certain rules to it.
Are free credit card generators real?
No. The numbers produced by the Credit Card Number Generator are real, in the sense that they conform to all the rules of a valid credit card number. That includes Luhn's algorithm - see more below. But these numbers aren't linked to any real credit card account, so there's no money for purchases.