What are the keyboard characters that NOT allowed to use as password?

Question

I'm building a random password generator, password strings would be generated from '!' to '~' according to ASCII table. I am wondering which char I should filter it out.

Answer 1

You can use anything you want. Some people use extended, invisible and multibyte chars.

The reason certain things are forbidden is sometimes because devs/admins don't want unnecessary trouble handling database-special chars (like ', ", *, %, - etc), messed up string delimiters, javascript or their back end code. Backslash (for example) can change the password unexpectedly and several chars can interfere with URL's.

Several things even look similar when written/alone, like the chars: lI1| or these: O0Q

You probably just want printable/typeable chars...which are ASCII 33 to 126.