Last updated
Common Use Cases
- Real-time validation in payment forms to catch typos before submission
- Displaying the correct card network logo as the user types
- Testing payment integrations with valid test card numbers
- Generating valid test card numbers for QA testing
- Understanding card number structure for payment form UX design
- Verifying that card numbers in test data are correctly formatted
The Credit Card Validator on TechConverter.me provides instant Luhn validation, card network identification, and step-by-step algorithm breakdown. Enter any card number to validate its structure and identify the network — no real card data is ever sent to a server.
Examples
Example 1: Luhn Algorithm Step-by-Step
Understanding how the Luhn check works helps developers implement their own validation. Here is the step-by-step calculation for a Visa test card number:
Card number: 4532015112830366
Step 1: Starting from the right, double every second digit:
Original: 4 5 3 2 0 1 5 1 1 2 8 3 0 3 6 6
Position: 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Double: 8 6 0 10 2 16 0 12 6
(even positions from right are doubled)
Step 2: For doubled values > 9, subtract 9:
10 → 1, 16 → 7, 12 → 3
Step 3: Sum all digits:
8 + 5 + 6 + 2 + 0 + 1 + 1 + 1 + 2 + 2 + 7 + 3 + 0 + 3 + 3 + 6 = 50
Step 4: Check if sum is divisible by 10:
50 % 10 = 0 ✓ VALID
Any card number where the final sum is not divisible by 10 is invalid. This catches most typos and random number entries.
Example 2: Card Network Identification by Prefix
The validator identifies the card network from the card number prefix:
Visa:
Prefix: 4
Length: 13 or 16 digits
Example: 4532015112830366
Mastercard:
Prefix: 51-55 or 2221-2720
Length: 16 digits
Example: 5425233430109903
American Express:
Prefix: 34 or 37
Length: 15 digits
Format: 4-6-5 (e.g., 3714 496353 98431)
Example: 371449635398431
Discover:
Prefix: 6011, 622126-622925, 644-649, or 65
Length: 16-19 digits
Example: 6011111111111117
JCB:
Prefix: 3528-3589
Length: 16-19 digits
Example: 3530111333300000
Example 3: Stripe Test Card Numbers
Developers testing Stripe integrations use specific test card numbers. The validator confirms these are valid Luhn numbers:
Stripe test cards (all pass Luhn check):
Successful payment:
4242424242424242 → Visa ✓ Valid
4000056655665556 → Visa (debit) ✓ Valid
5555555555554444 → Mastercard ✓ Valid
378282246310005 → Amex ✓ Valid
Declined cards:
4000000000000002 → Visa (generic decline) ✓ Valid Luhn
4000000000009995 → Visa (insufficient funds) ✓ Valid Luhn
4000000000000069 → Visa (expired card) ✓ Valid Luhn
Note: These numbers pass Luhn validation but are rejected
by Stripe's payment processor for testing specific scenarios.