Signing up to the PlayStation Network is free. Two types of accounts can be created: Master accounts and Sub accounts.[17] A master account allows full access to all settings, including parental controls. Sub accounts can subsequently be created (e.g. for children) with desired restrictions set by the master account holder.[18] A sub account holder has the option to upgrade their account once they reach 18 years of age.[19] Sony encourage registrants to use a unique email and strong password not associated with other online services.[20][21]