American Express and Diners Club are the two main card networks that start with 3
When you look at the first digit of a credit card number, it tells you which company issued the card. Cards starting with 3 come from American Express (usually starting with 34 or 37) or Diners Club (starting with 36 or 38). These are separate payment networks from Visa (which starts with 4) and Mastercard (which starts with 5).
The first digit is part of the card's Bank Identification Number, or BIN. This number helps merchants, banks, and payment processors route your transaction to the right place. Knowing which network your card belongs to matters because not every merchant accepts every type of card — some smaller businesses or certain online retailers may take Visa and Mastercard but not American Express.
American Express is by far the larger of the two networks. Diners Club still exists but is much less common in everyday use, though it remains accepted at many restaurants and travel-related businesses.
Key Takeaways
- American Express cards start with 34 or 37, while Diners Club cards start with 36 or 38.
- The first digit of your card number identifies the payment network, which determines where your transaction gets routed.
- American Express is widely accepted at most major retailers, but some smaller merchants may not take it.
- Diners Club cards are less common but still work at many restaurants, hotels, and travel merchants.
- You can find your card's network printed on the front of the card itself, not just in the number.
How American Express cards work differently
American Express operates as both a card network and an issuer — meaning American Express itself issues most of its cards, rather than working through banks the way Visa and Mastercard do. This is why American Express cards often come with different benefits and different fees than other cards.
American Express cards typically have higher annual fees but also offer rewards programs, travel protections, and purchase protections that can be more generous than what you find on Visa or Mastercard. The trade-off is that American Express charges merchants higher processing fees, so some smaller businesses choose not to accept it.
American Express cards come in several varieties: the basic Green Card, the Blue Card (often for everyday purchases), the Gold Card (with travel and dining rewards), and the Platinum Card (with premium travel and concierge benefits). Each has its own annual fee and reward structure.
Diners Club cards and where to use them
Diners Club is one of the oldest credit card networks — it predates both Visa and Mastercard. Today it is much smaller, but it still has a presence in the travel and hospitality industry. Diners Club cards are accepted at many hotels, restaurants, and airlines, particularly outside the United States.
In the U.S., Diners Club acceptance has shrunk over the years. Many everyday retailers do not accept it, so if you carry a Diners Club card, you should also have a Visa or Mastercard as a backup. Diners Club cards are often issued through partnerships with banks rather than directly by Diners Club itself.
If you are considering a Diners Club card, check the issuer's website to see which merchants accept it in the places where you shop and travel most. The network is still useful for business travel and international trips, but it is not a primary card for most people in the U.S.
Why the card number starts with 3
The card number system uses what is called the Luhn algorithm, a mathematical formula that helps prevent fraud. The first digit is the Major Industry Identifier, or MII. For credit cards, the MII is always 3, 4, 5, or 6. The second digit (or second and third digits together) then identifies the specific network.
This system has been in place since the 1960s and is maintained by the International Organization for Standardization. It is not random — each network is assigned a specific range of numbers so that payment processors can when ready recognize which network a card belongs to, even before they contact the issuing bank.
The remaining digits on your card encode your account number and a check digit that validates the entire number. This is why a card number is never truly random — it follows a specific structure that allows the payment system to work smoothly.
Checking which network your card belongs to
The easiest way to find out which network your card belongs to is to look at the front of the card itself. The network name — "American Express," "Diners Club," "Visa," or "Mastercard" — is printed clearly on the card, usually near the bottom or top.
You can also check your card number. If it starts with 34 or 37, it is American Express. If it starts with 36 or 38, it is Diners Club. You can find your card number on the front of the card or in your bank's online portal or mobile app.
If you have questions about your specific card's benefits, acceptance, or fees, contact the issuing bank or the card network directly. The customer service number is usually printed on the back of the card.
American Express acceptance in the U.S. and abroad
American Express is accepted at the vast majority of U.S. retailers, including grocery stores, gas stations, restaurants, and online merchants. However, some small independent businesses, certain gas stations, and a few regional chains do not accept it because of the higher processing fees American Express charges.
Internationally, American Express acceptance varies by country. It is widely accepted in Europe, Asia, and other developed nations, but in some regions Visa and Mastercard are more common. If you are traveling, check with your card issuer about acceptance in your destination before you leave.
American Express also offers travel protections and concierge services that can be useful when you are away from home. These benefits vary by card type, so review your card's terms to see what is included.
Frequently Asked Questions
Can I use a card starting with 3 everywhere?
American Express cards (starting with 34 or 37) are accepted at most major retailers and online merchants in the U.S., but some small businesses do not take them. Diners Club cards (starting with 36 or 38) have much more limited acceptance and should be paired with a Visa or Mastercard. Always check with the merchant if you are unsure.
Is American Express safer than Visa or Mastercard?
All three networks use similar fraud protection technology. American Express does offer strong purchase protection and dispute resolution, but Visa and Mastercard offer comparable protections. The safety of your card depends more on your bank's fraud monitoring and your own habits than on which network you use.
Why do some online stores not take American Express?
American Express charges merchants higher processing fees than Visa or Mastercard — typically 2.5% to 3.5% compared to 1.5% to 2.5% for other networks. Small online retailers with thin profit margins sometimes decline American Express to keep costs down. Larger retailers almost always accept it.
What is the difference between the card number and the network?
The card number is your unique account identifier. The network (American Express, Visa, Mastercard, Diners Club) is the payment system that processes your transaction. The first digit of your card number tells you which network it belongs to, but the full number is specific to your account.
Can I request a specific card network from my bank?
Your bank decides which network to use for each card product it offers. You cannot usually choose the network, but you can choose which card product to open — for example, your bank may offer both a Visa and an American Express card, and you can open whichever one you prefer.