Falsehoods programmers believe about phone numbers, especially American programmers, is probably its own separate article.

(Edited to add) This list is good, but is perhaps overly generous - it leaves off the most common irritant: programmers who believe that all phone numbers are exactly 10 digits, American-style, even if there is a country code dropdown.

https://github.com/google/libphonenumber/blob/master/FALSEHO...

One of the worst combinations of these falsehoods:

- Everyone has a usable phone number, a residential address that conforms to your validation criteria and can receive SMS - when transiting through an international airport and attempting to use the Wi-Fi.

- Everyone's phone number has a space in it

- Nobody's phone number has a space in it

Sometimes the phone-number input field won't let me type the last digit, unless I first remove the space. Sometimes it declares the number invalid if it doesn't have a space. The form never has hints as to what they consider a valid phone-number to look like.

- Every country is subdivided into states, or regions/provinces that work exactly like the american states.

Every time I encounter a mandatory "ZIP code" feature I use the one zip code that non-Americans are likely to remember: 90210.

Same here. If they ask for a full US address, I put 1 Sunset Blvd, Beverly Hills CA 90210 (not sure if that's actually a valid address, but in my experience plenty of web sites think it is).