Luhn Algorithm API: The Complete Guide

Need to validate numbers using the Luhn algorithm in your application? This guide covers everything you need to know about Luhn checksum validation via API, including how the algorithm works, common use cases, and implementation examples.

What is the Luhn Algorithm?

The Luhn algorithm, also known as the "modulus 10" or "mod 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers. It was created by IBM scientist Hans Peter Luhn in 1954 and is now a widely used error-detection method.

The algorithm can detect single-digit errors, as well as transpositions of adjacent digits (except 09 to 90 and vice versa).

How the Algorithm Works

The Luhn algorithm follows these steps:

Step 1: Starting from the rightmost digit

Double every second digit. If the result is greater than 9, subtract 9 from the result.

Step 2: Sum all digits

Add all the resulting digits together, including those that weren't doubled.

Step 3: Check the result

If the total modulo 10 equals 0, the number is valid.

Using the Luhn Algorithm API

TinyFn provides a simple endpoint to validate numbers using Luhn:

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

{
  "valid": true,
  "number": "4532015112830366",
  "checksum": 0,
  "check_digit": "6"
}

Parameters

Code Examples

JavaScript / Node.js

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

Python

import requests

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

cURL

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

Common Use Cases

• Credit Card Validation: Verify credit/debit card numbers
• IMEI Numbers: Validate mobile device identifiers
• National IDs: Some national identification numbers use Luhn
• Custom Identifiers: Generate check digits for your own numbering systems
• Data Entry Validation: Catch typos in numeric identifiers

Best Practices

1. Pre-filter input: Remove spaces and non-numeric characters before validation
2. Client-side first: Validate on client-side for immediate feedback
3. Combine with other checks: Luhn alone doesn't verify the number is real
4. Generate check digits: Use Luhn when creating your own ID systems