Luhn check

Validate a number's mod-10 check digit, or compute the digit for a prefix.

Checked in this browser. Nothing is sent anywhere.

Format check only — a passing number is not a real card or account. For form/QA test data, not payment processing. Up to 30 digits; spaces and dashes are ignored.

How to use

  1. Paste a number to validate it.
  2. Or enter a prefix to compute its check digit.
  3. Use only test numbers — never real cards.

What it supports

Format arithmetic only — a pass does not mean the number is real or usable. For QA and test data, not payments.

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