I have an input field on my website which uses pattern matching in the HTML
It needs to have
- Lowercase a-z (not upper)
- All numbers (0-9)
- Allows underscores (\_) but NOT spaces
- Minimum of 4 characters with a max of 12.
- Does not allow special characters such as @, #, $, %, ^, \* etc.

Right now I have pattern="(?=.\*[a-z0-9\_]).{4,12}"
The problem seems to be that it does allow special characters.