Credit Card Validator

How card validation works

Every payment card number includes a check digit calculated with the Luhn algorithm (mod-10). By running the same calculation, this tool confirms whether a number is internally consistent — catching typos and obviously fake numbers. The card's leading digits and overall length also reveal which network issued it.

A number that passes these checks is correctly formatted, but that does not mean it is a real, active or funded account — only the issuing bank can confirm that.

Supported card brands

• Visa, Mastercard and American Express
• Discover, Diners Club and JCB
• UnionPay

Safe for testing

All validation runs in your browser. Numbers are never transmitted, logged or stored — making this ideal for testing checkout forms with sample card numbers. Never enter real card details into tools you do not trust.

Key features at a glance

• Validates a card number with the Luhn (mod-10) checksum
• Detects the issuing brand from prefix and length
• Supports Visa, Mastercard, Amex, Discover, Diners Club, JCB, and UnionPay
• Built for testing and validation, never contacting a bank
• Catches typos and obviously invalid numbers instantly
• Runs in your browser — numbers are never transmitted, logged, or stored

How the Luhn algorithm works

The Luhn algorithm, also called the mod-10 checksum, is a simple formula that guards against accidental errors in identification numbers. Starting from the rightmost digit, every second digit is doubled; if doubling produces a number greater than nine, its digits are added together. All the resulting digits are summed, and if that total is divisible by ten, the number passes. The final digit of a card number is a check digit chosen specifically to make the whole number satisfy this rule.

Because of how it is constructed, Luhn reliably catches the most common human errors — a single mistyped digit or most simple transpositions of adjacent digits. That is exactly why it is used not just on payment cards but also on IMEI numbers and many national ID schemes. It is important to understand that Luhn is an error-detecting check, not a security measure; it confirms a number is well-formed, nothing more.

What card validation does not tell you

Passing the Luhn check and matching a known brand prefix means a number is correctly formatted and plausibly issuable, but it says nothing about whether the card is real, active, or funded. Only the issuing bank, through the payment network, can confirm that an account exists and has available credit. A validator like this one works purely on the number's mathematical structure and never communicates with any financial institution.

This distinction is why the tool is ideal for development and testing rather than fraud screening. Test card numbers published by payment processors are designed to pass Luhn so developers can exercise checkout flows without real money. For the same reason, you should never type genuine card details into tools you do not fully trust; legitimate format validation never requires sending the number anywhere.

Tips for using the validator

• Use it to test checkout forms with processor-provided sample numbers
• Treat a Luhn pass as 'well-formed', not 'real and active'
• Check the detected brand against the prefix you expect
• Never enter real card numbers into untrusted tools
• Validate client-side to catch typos before submitting a payment form

Why choose our credit card validator?

Our validator is completely free with no signup, no limits, and no subscription. All validation runs in your browser — numbers are never transmitted, logged, or stored — which makes it safe for testing checkout forms with sample card numbers.

It is one of more than 200 free tools on ToopTools, and you can pin it to your My Workspace, a personalized workspace where you keep the tools you use most in a single dashboard. Beside the other validation and security tools, it gives you a quick, private way to check card formats while you build and test payment flows.

Common use cases

Developers use the validator while building and testing checkout and billing forms, confirming that their own Luhn validation and brand detection behave correctly against known sample numbers. QA engineers use it to verify that invalid numbers are rejected and that each supported brand is recognized.

It is also useful for quickly identifying which network a number belongs to from its prefix, and as a teaching aid for understanding how the check digit and brand ranges work. Because everything stays in the browser, it is a safe sandbox for experimenting with card-number logic.

Is the credit card validator free?

Yes. It is completely free with no account, no sign-up, and no usage limits. Validate as many numbers as you like at no cost.

Does a valid number mean the card is real?

No. Passing the Luhn check and matching a brand only means the number is correctly formatted. It does not mean the card exists, is active, or has funds — only the issuing bank can confirm that.

Is it safe to enter a card number here?

The tool runs entirely in your browser and never transmits or stores numbers, so it is safe for sample and test numbers. As a rule, never enter real card details into any online tool you do not fully trust.

What is the Luhn algorithm?

It is a mod-10 checksum that uses a final check digit to detect accidental errors in a number. By doubling alternate digits and summing, it catches most single-digit mistakes and transpositions, which is why payment cards use it.

Which card brands are supported?

The validator detects Visa, Mastercard, American Express, Discover, Diners Club, JCB, and UnionPay from their characteristic prefixes and lengths.

Where can I get test card numbers?

Payment processors such as Stripe and PayPal publish official test card numbers that pass the Luhn check. Use those for development; they let you exercise checkout flows safely without real cards.

How do I check if a credit card number is valid?

Enter the card number and the tool instantly checks it with the Luhn algorithm and identifies the card brand. A pass means the number is mathematically well-formed — useful for catching typos in test data — though it does not mean the card actually exists.

Does the credit card validator work offline?

Yes. The check runs entirely in your browser, so once the page has loaded the tool works without an internet connection, and the number you enter is never uploaded, logged, or stored — it stays on your own device.