limiting usernames to A-Z(a-z) 0-9

[ethicks]

So I want to limit user name's (on sign-up) to only capitals (non-capitals) and numbers (0-9). I'm not exactly sure how to accomplish that...
any help would be appreciated.
Running v.3.8.4

[cellarius]

Try ^[a-zA-Z0-9]+$

I do not know what you mean by "only capitals (non-capitals)". That seems to be somewhat contradicitve...

[James Birkett]

I think I looked into this last time and found that using a regex won't work for limiting the case unless you go into the source and modify the code.

The code has been made case insensitive by default, I can't remember where I saw it.

*looks*

Limiting to only numbers and letters is accomplishable though:
^[a-zA-Z0-9]+$