Card Test Generator: Safe Sandbox Testing Guide
Use a card test generator only for sandbox payment testing. Learn safe steps, processor test cards, validation, and compliance limits.
Redeem your gift cards at any of our Merchants
Card Test Data Generator: Safe Test Card Numbers for Developers
You can purchase a gift card from any of these locations
Card Generator for Testing: What It Is and How to Use It Safely
Onyx Gift Cards is a Grenadian company designed to introduce, market and manage gift cards systems in Grenada for retailers and corporations. We are enthusiastic about the effect and influence we will have on the local market. We intend to expand our systems regionally with a range of product offerings and services.
Gift cards are the preferred way of giving and receiving gifts. They carry a monetary value that can be redeemed for gifts at your favorite store.
Onyx GiftCards are “Open Gift Cards” which means that they can be redeemed at multiple merchant locations. They are standard credit card size, can fit into the average wallet and made of PVC plastic. Onyx GiftCards are Barcoded for security and safety for the consumer and bear a disclaimer at the back.
Onyx Giftcards can be bought with a branded Card backer which is black in colour and is designed to fit the card. There is an area to write a brief message to the recipient as well.
A test credit card generator produces card numbers that pass the Luhn check digit test. The output is random digits with a valid checksum. No bank issues those numbers. No account backs them. Payment processors publish fixed test numbers for sandbox use, so a generator adds nothing for legitimate testing.
The Luhn algorithm is a mod-10 checksum. It catches one wrong digit and most swaps of two adjacent digits. It does not confirm that an account exists, that it holds funds, or that a card was ever issued. A 16-digit number with a correct final digit passes. That is the full test.
The first digits carry the issuer identity. Visa starts with 4. Mastercard uses 51 through 55 and 2221 through 2720. American Express uses 34 and 37 and runs 15 digits. Discover uses 6011 and 65. A generator copies those prefixes, fills the rest with random digits, then computes the check digit.
Every large processor ships a fixed list. Stripe uses 4242 4242 4242 4242 for a successful Visa charge and 4000 0000 0000 0002 for a decline. Adyen, Braintree, Square, and Checkout.com publish their own lists. Amex test numbers include 3782 822463 10005. These numbers work only against test API keys in a sandbox.
The CVC and expiry fields accept arbitrary values in most sandboxes. Some test suites require a specific CVC to trigger a specific decline code.
A live gateway sends an authorization request to the issuer through the card network. The issuer checks the account, the balance, the CVC, and the address verification data. A generated number has no account behind it, so the issuer returns a decline, often "invalid account number" or "no such issuer". Merchants see a burst of small declines.
Some people use generators to test stolen card data or to find numbers that slip past a weak checkout. That activity is card testing. It is a federal crime in the US under 18 U.S.C. § 1029, which covers the production, use, and trafficking of access devices. Card network rules treat it as fraud, and processors fine merchants who allow it. Sites that sell CVV data are selling stolen financial records. Buying or using them carries the same exposure. There is no legal path to testing a card you do not own.
Developers use test numbers to check form validation, tokenization, refunds, 3D Secure flows, and webhook handling. Use the list from your processor. Keep test keys out of production code. Never point test data at a live endpoint.