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Luhn Validator

Validate numbers using the Luhn algorithm (Mod 10). Check credit card numbers (Visa, Mastercard, Amex, Discover), IMEI numbers, and other identifiers. Step-by-step visualization of the doubling and reduction process. Generate valid check digits. Runs entirely in your browser — your data never leaves your machine.

luhn validator credit-card checksum mod10 imei verification

Published May 31, 2026

All interactive tools run entirely in your browser. Your data never leaves your device.

How It Works

Enter a number and the tool applies the Luhn algorithm: starting from the rightmost digit, every second digit is doubled. If the doubled value exceeds 9, subtract 9. Sum all digits — if the total is divisible by 10, the number is valid.

Features

  • Validate mode: check if a number passes the Luhn algorithm
  • Generate mode: compute the correct check digit for a partial number
  • Card type detection: automatically identifies Visa, Mastercard, Amex, Discover, Diners Club, JCB, IMEI
  • Step-by-step visualization: see the doubling, reduction, and summation for each digit
  • Flexible input: accepts spaces, dashes, and dots as separators
  • 5 preset examples: valid Visa, valid Mastercard, valid Amex, invalid number, IMEI
  • Private: all processing runs in your browser — no data transmitted

Use Cases

  • Verifying credit card numbers during payment integration testing
  • Checking IMEI numbers for mobile device identification
  • Understanding the Luhn algorithm for educational purposes
  • Generating valid test numbers with correct check digits
  • Debugging payment processing validation logic