I need a regex for checking if a Xbox Live Gamertag is valid:

Aa-Zz, 0-9, single spaces, can't start with a number (min 1, max 15)

I can't get it to not allow double spaces..

Any idea?

can a single space be a valid input? From your rules, as they are stated, it can.

if yes, then try this. Your regex engine must support look-arounds:

^(?!.*\x20{2})[A-Za-z\x20][A-Za-z\d\x20]{0,14}$

Thanks!

 It's for PHP. I don't know if it supports it, but I'll try it.

It does support it:

if (preg_match('/^(?!.* {2}|^\d)[A-Z\d ]{1,15}$/i',$sourcestring)) {

 // do something

} else {

 // do something else

}