Here is a list to help you learn about Undernet channel modes and User modes. They change with time, so check back every so often to be sure you are up to date.

User Modes

{Syntax: /mode nickname +/- mode(s)}

+d Deaf in all channels. You won't "hear" a thing that's said in the channels. Private messages do get through though. Primary reason is making the job easier for service bots that don't want to process channel messages.

+i Makes you invisible. Invisible people won't show up when searched for with /who, /who #chan and not with /whois with wildcards, unless you can see them already by sharing a channel. To put it briefly, the invisible mode prevents people from finding you unless they know your exact nickname or are on the same channel as you. You can hide by changing nick, people can't mass-message everyone on your ISP and you are not visible from outside a channel. Today more than half of the nicks on Undernet are +i. When not set to +i, a fellow user can locate you through the /who or through the /names #channelname command. IRC Operators also have the ability to see someone regardless of whether they are invisible or not.

+s Receives server notices. You receive various information sent between servers, mostly kills and G-lines, but also nickname collisions, invalid usernames, splits, etc. Setting yourself +s is a request to the server to send you all the generic server messages and information about oper kills. Undernet has stopped allowing regular users to use +s.

+w Receives wallops. The IRCops can broadcast messages with this. Wallops are network-wide messages sent by IRC Operators to each other. Any user who is set to +w will also be able to observe the conversation. Wallops have become quite extinct on Undernet and are rarely sent. However, Undernet did 'broadcast' the 10th Anniversary celebration on wallops, and may be used again for broadcasting large events.

+x is a usermode that allows logged in users to hide their real host, replacing it with Log into X (/msg login Username Password) then type //mode $me +x or /mode nick +x. Hiding your hostname will shield you against several types of attacks often carried out on IRC, but be aware that taking part in a DCC chat or file transfer will reveal your IP address. The +x usermode remains as long as you’re connected to the IRC server, so that channel service can recognize you even if your server splits off and rejoins the net. No need to login to X all over again.

Channel Modes

+o To op someone. A channel operator is designated by the @ next to their nick. Those with a @ can give and remove the +o mode.

+v To voice someone. When a channel is moderated (+m), only the channel ops and the channel voices can send messages to the channel. Only channel ops can add or remove voice.

+b To ban someone. +b stands for ban and allows a channel operator to deny a person (or a group of people) access to the channel. If someone is banned while in the channel, they will not be able to talk. Syntax: /mode #channelname +/-b [hosts] Example: /mode #mIRCHelp +b-bb *!* If you don't specify any hosts, you will be shown a list of channel bans, even if you're outside the channel.

+D A new channel mode, +D, has been added for auditorium-style channels. These are channels where most users listen but do not speak or receive ops or voice. The effect of +D is that the server waits to send the JOIN message for new users until the user gets ops or voice or sends a message to the channel. A list of join-delayed users in a channel may be retrieved by using /NAMES -d #channel. The response to /NAMES -d uses the same format as numeric 353, but uses numeric 355 instead. If an op removes +D while there are still join-delayed users, the server automatically sets mode +d, and removes +d when the last user's join is shown. It is not possible to set channel mode +d manually; its purpose is to warn channel users that there are "hidden" users in the channel.

+i Channel is invite-only. Setting a channel to invite only will only allow those who have been invited to the channel (with the /invite command) to join the channel. On undernet, you must have ops to invite someone into a channel. To do this, use: /invite nickname #channelname.

+k Channel is keyed or password protected. The key of the channel is a word that you must specify in your /join command when attempting to enter the channel. If the key was incorrect or if no key was specified then you will be denied access to this channel. Syntax: /mode #channelname +/-k key Example: /mode #mIRCHelp +k khaled Anybody joining the channel will need to use the /join #channelname key command. In this case, it would be /join #mIRCHelp khaled.

+l Channel is limited to participants at the same time. The channel limit allows you to specify the maximum number of users who can be in the channel at a time. Once this number has been reached, anyone who attempts to join the channel will receive an error message of the channel being full. Example: /mode #channelname +/-l number (/mode #mIRCHelp +l 25)

+m Channel is moderated. Only ops and voiced people can talk. A moderated channel only allows the ops (@) and voices (+) to send messages to the channel. All other messages will be blocked. Example: /mode #channelname +/-m

+n No messages or notices are allowed to be sent to the channel from anyone not in the channel. The +n stands for no external messages. If +n is not set then it's possible for someone to send messages to the channel even if they are not present inside the channel. On Undernet this mode is now almost universally used by channel operators. (/mode #channelname +/-n)

+p Channel is private. A private channel is not shown on the /whois output unless the person requesting the /whois is also on the channel. A /LIST command will not return anything for a +p channel. A display of /NAMES will return Prv: *" in place of the channel name, but the users will be listed. In other words, a private channel prevents people on the outside from finding out its name, not who is in it. (/mode #channelname +/- p)

+r Channel is restricted. +r is a channel mode where only users who are logged into X (i.e. have a registered username) can join the channel. The command to set it is: /mode #channel +r ... to unset it: /mode #channelname -r. The +r channel mode can be overridden with an invite to a +r channel.

+R Channel is registered. +R is a channel mode that will be operable once u2.10.12.pre13 is running on all servers. This mode will enable basic communication between X and C. In all registered channels, X will set +R, enabling C to know not to act on that channel. Pre-u2.10.12.pre13, C identifies a registered channel by the presence of X actually on the channel. This means C is incorrectly acting on registered channels where X isn't on the channel for some reason. This mode will also make it easier for users and possibly other services to easily identify a registered channel without having to /msg X.

+s Channel is secret. The only difference between a secret (+s) channel and a private (+p) channel is that you can do "/topic #channel" for +p channels from outside. (/mode #channelname +/-s) And, you will get a result with /who #channelname if the channel is +s.

+t Topic change by ops only. No one but the ops can change the channel topic. (/mode #channelname +/-t)