I could be wrong, but I remember reading some S3 users stating it didn't work. It does work on the ATT S4 but ONLY on the NEWEST NC1 firmware update that came out (4.4.2) but did NOT work on the previous NB1 firmware (also 4.4.2).
It is worth a try as it will NOT brick your phone. If it doesn't work it will just let you know it is not rooted.
Sent From My Spiderman,Ironman,Red,Dark Blue,Green, GreyedOut BadAss Themed I337