Redact Credit Card Numbers
Find and redact credit card numbers in your text. Uses Luhn validation to avoid false positives.
About Redact Credit Card Numbers
Credit card numbers in text are dangerous to share — they can be lifted by scrapers, archived by services, or simply seen by the wrong reader. This tool finds 13–19 digit sequences and (by default) validates them with the Luhn checksum so it doesn't flag random ID numbers as cards. Matches are replaced with a redaction marker.
When to use it
- Scrubbing card numbers from log lines or support tickets
- Preparing transcripts for sharing without PCI exposure
- Auditing data dumps for sensitive payment information
How it works
A regex matches sequences of 13–19 digits with optional spaces or dashes between them. Each match's digits are extracted and checked against the Luhn algorithm — a checksum every real credit card number satisfies. Only valid Luhn matches are redacted by default, but the check can be disabled to redact every digit-shaped string.
Examples
Card 4532 0151 1283 0366 on file.
Card [CARD] on file.
Frequently asked questions
- What is the Luhn algorithm?
- A simple checksum on the last digit of a card number. It catches single-digit typos and randomly-generated sequences while passing on real card numbers. Every major card brand (Visa, MasterCard, Amex, Discover) uses it.
- Can I disable Luhn validation?
- Yes — toggle 'Luhn validation' off to redact any 13–19 digit sequence regardless of checksum. Useful when working with test cards or internal IDs that look card-shaped.
- Does this replace the need for proper PCI compliance?
- Absolutely not. It's a redaction utility for content you've already collected. Real PCI handling requires designing your system never to receive or log card data in the first place.