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Disclaimer: Do not use any credit card numbers, except your own, to use on the internet. It’s illegal to use other people’s credit card numbers to purchase your own stuffs. Free credit card numbers featured in this post is written purely to test one’s knowledge to see if these are valid. It should be viewed from a purely academic perspective.

Credit card is a mystery combination of random numbers that allows you to purchase something without taking out cash from your pocket, magic eh? But do you know how those numbers are calculated? If they are not valid, how can you detect it? Easy, just apply the Luhn check and you will start to discover those fake credit card numbers!

1. Starting with the check digit (Which is the last digit of a credit card), double the value of every second digit (from right to left). E.g. For a 16 digit credit card number, double the 15th, 13th, 11th, 9th…digits (Digits in odd places). It sums up to a total of eight numbers.

2. If doubling of a number results in a two digit number, add up the digits to get a single digit number. This will result in eight single digit numbers.

3. Now, replace the digits in the odd places of the original credit card number with these new single digit numbers and you will get a new 16 digit number.

4. Add up all the digits in this new number. If the final total is perfectly divisible by 10, then the credit card number is valid (Luhn check is satisfied), else it is invalid.

Yeah, I know it’s a bit confusing, that’s why I have created more examples using these images, have a look and you will understand it very soon:

First example was done using a MasterCard credit card :

Note that the credit card number starts with the letter 5, so that means the card is issued by MasterCard. To determine whether it’s a valid credit card number, I have included the image together with the workout:

As what you have seen, the total sum of the credit card numbers using the doubled digits is 66, which means it cannot be divided completely by 10, thus it is invalid.

Let’s take another example using a Visa credit card :

As what you have seen, the total sum of the credit card numbers using the doubled digits is 35, which means it cannot be divided completely by 10, thus it is invalid.

ENDING

If you have made this far, here are some additional points to be remembered. Free credit card numbers don’t mean that you can use it to purchase items anywhere, these are experiments for E-Commerce owners to test if their system is fully functional. Millions, billions or even trillions of numbers can be generated using the Luhn Check. If you successfully get one working number, you still need to type in the CVV and personal details to verify that you are the owner of the credit card, so work harder and apply for a credit card

Think you have learned what I have taught you? Try these test from Paypal and see if you can get all the answers correct.

Additional Resources :
Card Identification Features (pdf file) – Explanation of different credit cards by several credit card companies.

Credit Card Numbers and Credit Card Generator by Graham King. Great resource for E-Commerce owners

Anatomy of Credit Card Numbers by Merriam Park

Credit Card Number – Wikipedia.

Image via Paylife and UMS Alumni

Tagged as: Card, Credit, Exam, Free, Mastercard, Numbers, Test, Valid, Visa