To prevent öäüÖÄÜß just use this: _Inputmask_add($MyInputField, "[\x{00c4} \x{00e4} \x{00d6} \x{00f6} \x{00dc} \x{00fc} \x{00df}]", 500)The idea with the unicode was close
In another Input field I disallow semicolon and some other characters with _Inputmask_add($MyInputField, "[; p P a A]", 500)and it works. Just with Umlauts it did not work.
How can I prevent Umlauts from being inserted into input fields? I tried the following, but it did not work: _Inputmask_add($MyInputField, "[öäüÖÄÜ]", 500)