The NICK command lets a user set and change their nickname. When the command is sent from a user to a server, it’s a nickname change request (which the server can accept or deny). When the NICK message is sent from the server, it indicates a change that has taken place.

NICK <nickname>
  • <nickname>: The nickname to change to.

If <nickname> is longer than the server allows nicknames to be, it is silently truncated (the user should find and set the new nickname from the reply)

This command can be used at two times – during initial connection registration to set the client’s initial nickname, and after registration to change their nick. When used during registration, the server will silently accept the user’s request (or reply with an appropriate error numeric). If used after registration, the server will return a NICK message or appropriate error numerics.

If the desired nickname is already in use, the server returns an ERR_NICKNAMEINUSE numeric and rejects the change. If the desired nickname is invalid (e.g. contains invalid characters), the server returns an ERR_ERRONEUSNICKNAME numeric and rejects the change. If the client does not send the <nickname> parameter, the server returns the ERR_NONICKNAMEGIVEN numeric.

The NICK message is also sent by servers to note the change of another user’s nickname – in which case the format remains the same but the message’s <prefix> contains the original details of the user. The examples illustrate this in more detail. Similarly, when a nickname change is performed, servers notify all clients that are in the same channels with an appropriate NICK message as described.


C  ->  NICK dan
C  ->  USER d 0 * :Dan!
S <- 001 dan :Welcome to the ExampleNet Internet Relay Chat Network dan

Successful connection registration

C  ->  NICK ben
C  ->  USER b 0 * :Benno!
S <- 433 * ben :Nickname is already in use.
C  ->  NICK ben-
S <- 001 ben- :Welcome to the ExampleNet Internet Relay Chat Network ben-

Connection registration with nick-in-use

C  ->  nick 345gman!
S <- 432 george 345gman! :Erroneous Nickname

Invalid nickname

S <-   :[email protected] NICK :dan
S <-   :[email protected] NICK :danny
S <-   :[email protected] NICK :george

Series of nickname changes seen by another user on the network

C  ->  nick dan-is-my-name-dont-wear-it-out-at-all
C  ->  user d 0 * :Danny
S <- 001 dan-is-my-name-dont-wear-it-ou :Welcome to the ExampleNet Internet Relay Chat Network

Silently truncated nickname during registration

C  ->  NICK my-name-is-george-it-is-a-really-cool-name
S <-   :[email protected] NICK :my-name-is-george-it-is-a-real

Silently truncated nickname after registration


Related Numerics


Contributors to this page: Daniel Oaks

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Latest change: 14 July 2020.