Designing and developing user interfaces in digital products 🧑‍💻


The stupidest validation rules

Recently I wrote a book about forms usability, and I paid special attention to validation because this topic is sensitive to me.

I've been developing user interfaces for over 10 years, and almost in every project, my customers asked to put some validation on an input that didn't make sense.

I've made a small collection of the funniest, weird and stupid validation rules that I've recently found. And included some useful links at the end.

As it turned out, most of the frustrating validation rules are about user names.

The purpose of this is to make you think twice before putting extra validation rules. Because after all, if you're not making some kind of analytics application that needs very strict data collected, in most cases it's okay to let the user put what they want. It's your responsibility to parse it and correctly interpret it.


A twitter screenshot where a person says that he worked on a projects where they required at least 5 characters for first name
They just haven't seen this list of two-letter names

A case when a register form allowed plus sign in the email field, but didn't allow it in the login form
Just don't pay the bills

An input that doesn't allow spaces in the user name
Well... not sure which letter is "not English"

An input that doesn't allow question mark as a symbol in the book name field
Book names can't have a question mark in their title?

Another case of restricting space symbol in name field
Obviously, the first name cannot consist of two words, right?

A code sample restricting first name up to 12 characters
At least they saved some bytes in the database

An example of not literate language
Looks like "literate" validation error

An example of a lot of errors displayed at once. One of them is asking for at least 5 characters for the first  name
Looks like there are some errors, huh? Poor "Har", he/she should've changed their name to fit the form rules :(

An example when the air company doesn't accept French language characters, even thought they are used in  user's passports
This time you won't take a flight

Valid zip code is marked as invalid
I don't live in the US, but I suspect that it might be a valid zip code, right?

Absence of date of birth validation
Not every site have strict validation rules though

Not trimming input results in an error, even though visually the email field looks fine
Found my own example. They don't know what does "trim" mean

Placeholder says that the field is option, while validation requires it to be filled in.
To be or not to be ©. I mean, optional or not optional?

Some useful links about validation

Falsehoods Programmers Believe About Names ( that's really awesome, even though dated 2010)

Designing Better Inline Validation UX ( my own note: Smashing Magazine is one of the best resources ever for a high quality content)

How to Report Errors in Forms: 10 Design Guidelines ( NNGroup is another solid company that does a lot of UX research. I would say NNGroup & SmashingMagazine are one of the best in this area)

Collection of useful do/donts cards for validation rules

My own article on about validation (also posted on this blog)

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