Credit Card Validator API: The Complete Guide

Need to validate credit card numbers in your application? This guide covers everything you need to know about credit card validation via API, including the Luhn algorithm, card type detection, and implementation examples in multiple languages.

What is Credit Card Validation?

Credit card validation is the process of verifying that a credit card number is structurally valid before processing a payment. This includes checking the card number format, verifying the Luhn checksum, and identifying the card type (Visa, Mastercard, American Express, etc.).

A typical credit card number follows this pattern: 4532015112830366 (Visa)

How Credit Card Validation Works

Credit card validation involves several checks:

Luhn Algorithm

The Luhn algorithm (also known as the modulus 10 algorithm) is a checksum formula used to validate credit card numbers. It detects single-digit errors and most transpositions.

Card Type Detection

Different card networks use specific prefixes and lengths:

• Visa: Starts with 4, 13-19 digits
• Mastercard: Starts with 51-55 or 2221-2720, 16 digits
• American Express: Starts with 34 or 37, 15 digits
• Discover: Starts with 6011, 6011, 644-649, or 65, 16-19 digits

Using the Credit Card Validator API

TinyFn provides a simple endpoint to validate credit card numbers:

GET https://api.tinyfn.io/v1/validate/credit-card?number=4532015112830366
Headers: X-API-Key: your-api-key

{
  "valid": true,
  "card_type": "visa",
  "card_number_masked": "4532********0366",
  "luhn_valid": true
}

Parameters

Code Examples

JavaScript / Node.js

const response = await fetch(
  'https://api.tinyfn.io/v1/validate/credit-card?number=4532015112830366',
  { headers: { 'X-API-Key': 'your-api-key' } }
);
const result = await response.json();
console.log(result.valid); // true
console.log(result.card_type); // "visa"

Python

import requests

response = requests.get(
    'https://api.tinyfn.io/v1/validate/credit-card',
    params={'number': '4532015112830366'},
    headers={'X-API-Key': 'your-api-key'}
)
result = response.json()
print(result['valid'])  # True
print(result['card_type'])  # "visa"

cURL

curl "https://api.tinyfn.io/v1/validate/credit-card?number=4532015112830366" \
  -H "X-API-Key: your-api-key"

Common Use Cases

• E-commerce Checkout: Validate card numbers before submitting to payment gateway
• Form Validation: Provide instant feedback on payment forms
• Data Cleaning: Verify card numbers in existing databases
• Fraud Prevention: Detect obviously invalid card numbers early
• Payment Processing: Pre-validate before expensive API calls to payment processors

Best Practices

1. Client-side validation: Validate card format before server submission to improve UX
2. Never log full card numbers: Always mask card numbers in logs and displays
3. Use HTTPS: Always transmit card data over encrypted connections
4. PCI Compliance: Ensure your application follows PCI DSS requirements