JCB — easy to omit, easy to fix.
JCB's format is one of the simplest to support correctly. It's also one of the most commonly forgotten entirely if your primary market isn't Japan or broader Asia.
JCB's Number Structure
| Property | Value |
|---|---|
| Prefix | 3528–3589 |
| Length | 16 digits |
| Grouping | 4-4-4-4 |
| Security code | 3-digit code, printed on the back |
| Primary market | Japan, with broader acceptance across Asia |
Structurally, JCB is one of the more straightforward networks to support: 16 digits, standard 4-4-4-4 grouping, and a conventional 3-digit security code — the same shape as Visa and Mastercard, just a different prefix window.
A Bit of History
JCB — originally Japan Credit Bureau — was founded in 1961 by Sanwa Bank and Nippon Shinpan, making it Japan's first domestically developed card network. It shares its leading digit (3) with American Express and Diners Club, all three falling under the same Major Industry Identifier category for travel and entertainment, even though JCB's specific 3528–3589 range doesn't overlap with either of theirs.
Why JCB Gets Skipped Entirely
Unlike Amex or Discover, JCB rarely causes a validation bug — it's structurally simple enough that a generic 16-digit, Luhn-based validator handles it correctly by accident, provided the prefix is in a recognized list at all. The far more common issue is that JCB isn't in that list in the first place, because a team building primarily for a US or European market may never have tested against it, or even known to. If you process payments from customers in Japan or elsewhere in Asia, it's worth an explicit line item in your test plan rather than an assumption that "generic 16-digit handling" already covers it.
Generating JCB Test Numbers
Select JCB from the Card Network dropdown above to generate a correctly formatted, Luhn-valid 16-digit number in the 3528–3589 range — useful specifically for confirming your network-detection logic recognizes JCB at all, not just that it handles the number once recognized.
Related Guides
Frequently Asked Questions
Is JCB hard to support technically?
No — it's one of the structurally simplest networks to support: standard 16-digit length, conventional 4-4-4-4 grouping, and a normal 3-digit security code. The challenge is usually that it's missing from the recognized prefix list entirely, not that it behaves unusually once recognized.
Does JCB use the same Luhn checksum as other networks?
Yes — JCB numbers follow the identical Luhn algorithm and ISO/IEC 7812 structure as Visa, Mastercard, and every other major network.
Who actually needs to test against JCB specifically?
Any business processing payments from customers in Japan or elsewhere in Asia, where JCB has meaningful market share. For a purely US- or Europe-focused business, it's lower priority, but still worth knowing your validator doesn't silently reject it if a JCB card ever does show up.