Channel Modes (cmodes)

Changing channel modes is an operation restricted to channel operators, who can be recognized by the @-prefixed to their name. They mostly regulate access and moderation.

Channel modes can be permanently set for registered channels through ChanServ:

/msg ChanServ set mlock <#channel> <+-cmode>

Available cmodes can be queried via:

/quote HELP CMODE
MODE <channel> <+|-><modes> [parameters]

? designates that the cmode is provided by an extension
and may not be present on this server.

CHANNELMODE - DESCRIPTION
------------------------------------------------------------------------
NO PARAMETERS:
     +n     - No external messages.  Only channel members may talk in
              the channel.
     +t     - Ops Topic.  Only opped (+o) users may set the topic.
     +s     - Secret.  Channel will not be shown in /whois and /list etc.
     +p     - Private.  Disables /knock to the channel.
     +m     - Moderated.  Only opped/voiced users may talk in channel.
     +i     - Invite only.  Users need to be invited or match a +I to
              join the channel.
     +r     - Registered users only.  Only users identified to services
              may join.
     +c     - No color.  All markup (color, bold, underline, etc.) in
              messages is stripped.
     +g     - Free invite.  Everyone may invite users.  Significantly
              weakens +i control.
     +z     - Op moderated.  Messages blocked by +m, +b and +q are instead
              sent to ops.
     +L     - Large ban list.  Increase maximum number of +beIq entries.
              Only settable by opers.
     +P     - Permanent.  Channel does not disappear when empty.  Only
              settable by opers.
     +F     - Free target.  Anyone may set forwards to this (otherwise
              ops are necessary).
     +Q     - Disable forward.  Users cannot be forwarded to the channel
              (however, new forwards can still be set subject to +F).
     +C     - Disable CTCP. All CTCP messages to the channel, except ACTION,
              are disallowed.
  ?  +O     - IRC Operator only channel.
  ?  +A     - IRC server administrator only channel.
  ?  +T     - No NOTICEs allowed in the channel.
  ?  +S     - Only users connected via SSL/TLS may join the channel while this
              mode is set. Users already in the channel are not affected.

WITH PARAMETERS:
     +f     - Forward.  Forwards users who cannot join because of +i,
              +j, +l or +r.
              PARAMS: /mode #channel +f #channel2
     +j     - Join throttle.  Limits number of joins to the channel per time.
              PARAMS: /mode #channel +j count:time
     +k     - Key.  Requires users to issue /join #channel KEY to join.
              PARAMS: /mode #channel +k key
     +l     - Limit.  Impose a maximum number of LIMIT people in the channel.
              PARAMS: /mode #channel +l limit
     +v     - Voice.  Allows a user to talk in a +m channel.  Noted by +nick.
              PARAMS: /mode #channel +v nick
     +o     - Op.  Allows a user full control over the channel.
              PARAMS: /mode #channel +o nick
     +b     - Ban.  Prevents a user from entering the channel, and from
              sending or changing nick if they are on it, based on a
              nick!ident@host match.
              PARAMS: /mode #channel +b nick!user@host
     +q     - Quiet.  Prevents a user from sending to the channel or changing
              nick, based on a nick!ident@host match.
              PARAMS: /mode #channel +q nick!user@host
     +e     - Exempt.  Allows a user to join a channel and send to it even if
              they are banned (+b) or quieted (+q), based on a nick!ident@host
              match.
              PARAMS: /mode #channel +e nick!user@host
     +I     - Invite Exempt.  Allows a user to join a +i channel without an
              invite, based on a nick!user@host match.
              PARAMS: /mode #channel +I nick!user@host