Credit Card Validator
Validate credit card numbers in your browser using the Luhn algorithm and detect the brand (Visa, Mastercard, Amex, Discover, Diners, JCB, RuPay)
About Credit Card Validator
Overview
The Credit Card Validator checks whether a credit or debit card number is structurally correct using the Luhn checksum and brand-specific length and prefix rules. It detects the card brand from the number itself, including Visa, Mastercard, American Express, Discover, Diners Club, JCB, and RuPay, then formats the number into readable groups as you type. Everything runs entirely in your browser. No card number ever leaves your device, no network call is made, and nothing is stored, which makes the tool safe to use with sample numbers during development and testing.
Features
- Pure client-side Luhn checksum validation with no network calls
- Automatic brand detection for Visa, Mastercard, Amex, Discover, Diners Club, JCB, and RuPay
- Smart grouping that switches to 4-6-5 for Amex and 4-6-4 for Diners
- Length validation per brand (for example 15 digits for Amex, 16 for Mastercard)
- Clear pass or fail reasons when a number is invalid
- Stat tiles for brand, digit count, length match, and Luhn status
- One-click test numbers for every supported brand
- Live mode that revalidates as you type and a manual mode with a single primary button
- Strict numeric input only — letters and other characters are stripped automatically
- Responsive layout and full dark mode support
How to Use
- Type or paste a credit card number into the input field
- Watch the digits group automatically and the detected brand appear
- Read the status alert to see whether the number passes Luhn and length checks
- Use the stat tiles for a quick view of brand, length, length match, and Luhn result
- Click one of the test card buttons to load a publicly known sample number
- Turn Live Mode off if you would rather press the validate button manually
FAQ
Does this tool check if a card actually works?
No. It only verifies that the number has a valid structure and passes the Luhn checksum. It cannot tell whether the card is real, active, or has funds, since that would require contacting a bank or payment processor and this tool never connects to a network.
Is it safe to paste my real card number here?
The number stays in your browser and is not sent anywhere, so the tool itself is safe. Even so, the habit of pasting real cards into validators online is risky. Use the built-in test numbers for development and reserve real cards for actual payment forms you trust.
What is the Luhn algorithm?
The Luhn algorithm is a simple checksum invented by Hans Peter Luhn at IBM in 1954. It doubles every second digit from the right, adjusts results above nine, then checks that the sum is divisible by ten. It is used by credit cards, IMEI numbers, and many ID schemes to catch typing mistakes.
Why is my valid-looking number marked invalid?
Common reasons are a digit typo that breaks the Luhn check, a digit count that does not match the brand (for example 16 digits for an Amex), or a prefix the tool does not recognise. Read the reasons in the red alert to see exactly which rule failed and adjust the number.
Which card brands does the tool detect?
It detects Visa, Mastercard (including the 2-series BIN range), American Express, Discover, Diners Club, JCB, and RuPay. Brand detection is based on published prefix ranges and total length rules, so cards from regional networks not in this list may show as Unknown even when their Luhn checksum passes.
Why does the spacing change for some cards?
American Express numbers are traditionally written as four, then six, then five digits, and Diners Club as four, six, four. Other major brands use four groups of four. The validator detects the brand from the first digits and applies the matching grouping while you type.