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.
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 dev.to about validation (also posted on this blog)