NickServ lets you record a nick and prevent others from using it.
NickServ help to register your nickname  

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ChanServ BotServ OperServ NickServ 


Sintaxe:  /msg NickServ HELP command.
NickServ allows you to "register" a nickname and prevent others from using it. The following commands allow for registration and maintenance of nicknames; to use them, type /msg NickServ command.
For more information on a specific command, type

/msg NickServ HELP command

REGISTER Registers your nickname in the NickServ database.
IDENTIFY Tells NickServ that you are really the owner of this nick.


Sintaxe:  /msg NickServ REGISTER password email
Registers your nickname in the NickServ database. Once your nick is registered, you can use the SET and ACCESS commands to configure your nick's settings as you like them. Make sure you remember the password you use when registering - you'll need it to make changes to your nick later. (Note that case matters! ANOPE, Anope, and anope are all different passwords!) Guidelines on choosing passwords: Passwords should not be easily guessable. For example, using your real name as a password is a bad idea. Using your nickname as a password is a much worse idea ;) and, in fact, NickServ will not allow it. Also, short passwords are vulnerable to trial-and-error searches, so you should choose a password at least 5 characters long. Finally, the space character cannot be used in passwords. The parameter email is optional and will set the email for your nick immediately. However, it may be required on certain networks. Your privacy is respected; this e-mail won't be given to any third-party person. This command also creates a new group for your nickname, that will allow you to register other nicks later sharing the same configuration, the same set of memos and the same channel privileges. For more information on this feature, type /msg NickServ HELP GROUP.
/msg NickServ REGISTER mypass


Sintaxe:  /msg NickServ IDENTIFY password
Tells NickServ that you are really the owner of this nick. Many commands require you to authenticate yourself with this command before you use them. The password should be the same one you sent with the REGISTER command.
/msg NickServ IDENTIFY mypass