Regex for IBAN allowing for white spaces AND checking for exact length

Question

I need to check an input field for a German IBAN. The user should be allowed to leave in white spaces and input should be validated to have a starting DE

Answer 1

Most simple solution I can think of:

^DE(\s*[[:alnum:]]){20}\s*$

In particular, your initial [DE]{2} is wrong, as it allows 'DD', 'EE', 'ED' as well as the intended 'DE'.