Issuer identification
The first digits give it away
Before you have typed even half a card number, the opening digits already say which network issued it. That is how checkout pages swap in the right logo while you type. Pick a network to see its rules.
CID: 4 digits, on the front. Move your pointer over the card.
- Starts with
- 3437
- Length
- 15 digits
- Security code
- CID, 4 digits
- Luhn check
- Always applied. The last digit is the check digit.
Anatomy of a card number
The sandbox American Express number below, split by what each part means. The numbers are public test data, not a real account.
378282246310005
- 1st digit
Major industry identifier. Here it is 3: travel and entertainment.
- First 6 digits
Issuer identification number (IIN), often called the BIN. It names the network and the bank. The standard grew to 8 digits in 2022, though many systems still read 6.
- Middle digits
The account identifier, chosen by the bank. It means nothing outside of it.
- Last digit
The Luhn check digit, worked out from all the digits before it.
All the networks at a glance
| Network | Starts with | Length | Code |
|---|---|---|---|
| American Express | 34, 37 | 15 | CID (4) |
| Visa | 4 | 13, 16, 19 | CVV (3) |
| Mastercard | 51-55, 2221-2720 | 16 | CVC (3) |
| Discover | 6011, 644-649, 65, 622126-622925 | 16-19 | CID (3) |
| Diners Club | 300-305, 3095, 36, 38, 39 | 14-19 | CVV (3) |
| JCB | 3528-3589 | 16-19 | CVV (3) |
| UnionPay | 62 | 16-19 | CVN (3) |
| Maestro | 5018, 5020, 5038, 5893, 6304, 6759, 6761-6763 | 12-19 | CVC (3) |
These are the publicly documented ranges. Networks add and retire ranges, a few overlap (UnionPay's 62 also covers part of Discover's range, so the narrower range wins), and Maestro prefixes change often. For anything that moves money, ask your payment provider.