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ToolWrenValidate a card or ID number against the Luhn checksum and detect the likely card type.
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Luhn Check is a free, private online tool that lets you check whether a number passes the Luhn checksum used by credit cards and IMEIs. It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
The Luhn algorithm is a checksum formula that catches accidental errors in numbers like credit cards, IMEIs and some IDs.
It reports whether the number passes the check, how many digits it has, and the likely card brand from its prefix.
Passing Luhn means the number is well-formed, not that it's a real, active card. It validates format only.
The Luhn algorithm is a simple checksum formula that detects accidental errors in identification numbers - most famously credit card numbers, but also IMEIs and some national IDs. This tool checks whether a number passes the Luhn test and identifies the likely card type from its opening digits.
Starting from the right, every second digit is doubled (and if the result exceeds 9, its digits are added together, or equivalently 9 is subtracted). All the digits are then summed, and if that total is divisible by 10, the number passes. This clever scheme catches the most common human errors - single mistyped digits and most transpositions of adjacent digits.
Passing the Luhn check only means a number is well-formed - it has a valid checksum. It does not mean the card or account actually exists, is active, or has funds. Real validation requires the issuing network. Luhn is purely a first-line sanity check to catch typos before a number is submitted for real processing.
Online checkout forms use Luhn to flag mistyped card numbers instantly, before contacting the payment network - improving the user experience and reducing failed transactions. It also validates IMEI device identifiers and various government and corporate ID schemes. The card-type detection here uses the well-known prefix ranges (Visa starts with 4, Mastercard 51-55, and so on).
Paste a number (spaces and dashes are ignored) and the tool reports pass or fail, the digit count, and the detected card type. Because it runs entirely in your browser, you can check numbers without anything being sent to a server - though you should never enter real, live card details into any tool unnecessarily.