The Username plugin helps to change username, only if username is not exist and without effecting others user's username.
The Username plugin helps to change username of admin, without effecting other user's username. First it will check if same username is exist or not. if same username is not exist, then only it will update existing user's username. Every administrator can change only his/her username from admin panel.
After activation there is a sub menu in Settings called Username. Click on this and there is an option to change Username. Insert your new username and then in settings there is an option Click to check username is exist or not Click and check user is exist or not. If username already exist then it will alert you as Username In Use! in red color, else it will alert you Username Not In Use! in green color. If username is not exist and user click on submit then it will update username and it will redirect to login page. Now login with new username.
Note Password remains same. It is completely safe. If you are not redirect to login page that means Username is not changed.