Visa test card numbers, and the format behind them.
Visa is the format most validators are built around by default — 16 digits, starting with 4. Here's the actual structure behind that assumption.
Visa's Number Structure
| Property | Value |
|---|---|
| Prefix | Always starts with 4 |
| Length | 16 digits (13-digit legacy cards still exist but are rare) |
| Grouping | 4-4-4-4 |
| Security code | 3-digit CVV2, printed on the back |
| Network model | Open-loop — Visa licenses the network to many issuing banks |
The first six to eight digits form the BIN/IIN (Bank Identification Number), which identifies the specific issuing bank — Visa itself doesn't issue cards directly, unlike the closed-loop model American Express uses.
Why Visa Is the Default Assumption
Because Visa is the most widely issued network globally, a huge number of card-input forms and validation libraries are built with Visa's format as the implicit baseline — 16 digits, 4-4-4-4 spacing, 3-digit CVV. That's a reasonable starting point, but it's also exactly why testing against a different format (Amex's 15 digits and 4-digit CID, for instance) catches bugs that Visa-only testing never will.
Generating Visa Test Numbers
Select Visa from the Card Network dropdown in Luhnly's generator above to produce Luhn-valid 16-digit numbers starting with 4, correctly formatted and paired with a 3-digit CVV — useful for UI and form-validation testing upstream of whichever payment processor you're integrating with.
Related Guides
Frequently Asked Questions
How many digits does a Visa card number have?
16 digits for virtually all modern Visa cards. A small number of legacy 13-digit Visa cards still exist but are increasingly rare.
Does Visa issue cards directly?
No — Visa operates an open-loop network, meaning it licenses its payment rails to many separate issuing banks, which are the actual card issuers. This differs from American Express's closed-loop model.
What's the difference between Visa's CVV and CVV2?
CVV2 is the 3-digit code printed on the back of the card, used specifically for card-not-present transactions like online purchases. The original CVV is encoded on the card's magnetic stripe and isn't something a cardholder can see.