I just checked. I have three AMEX cards (Platinum, Blue Cash Preferred, Green) in my wallet. All three have both four-digit numbers on the front as well as three-digit numbers on the back.

I don't recall ever being asked for the three-digit code on the back (like I am with most VISA/MasterCard credit cards). It's always the four-digit one on the front.

The Apple Store (as in, the actual brick and mortar establishment) started using the 3-digit code on the back of my American Express card at some point instead of the 4-digit one at the front (but they are so far the only company I have personally run into which does that).

It does - there is a 3 digit number on the back in the signature strip. The Amex website will ask you for it if you attempt to change your phone number, amongst other similar high-risk transactions.

Not on mine there isn't. This may be a US-only thing?

Some discussion, which doesn't shed a whole lot of light though: https://insideflyer.com/forums/threads/what-is-the-3-digit-c...

At least most Spanish credit cards use the 3-digits code on the back of the credit card. And it's almost always asked for (but not in amazon iirc).

All of my UK Amex cards have it.

I have been asked the 3 digit code when booking an airline ticket on a non-US site. During payment it passed through a amex safekey site which I think is kind of like 3d secure

http://security.stackexchange.com/a/136296

Old comment, sorry, but I think AMEX codes are on the front of the card.