Sometimes, you may encounter false negatives regarding credit cards. That’s because usually, the font they use for the numbers makes the 1’s and 7’s really similar. So, our algorithm may detect the credit card, but deem it invalid because Luhn algorithm didn’t pass. Our API will draw a red rectangle if it believes this to be the case, so you can take proper action. If you want all credit card numbers, valid and invalid, to be redacted, simply set redact_possible_cc to true.