Internet Relay Chat was created in 1988 and has hardly changed. It can be used to exchange text messages (one message = single line) with other people, either privately (called query, PM, private message, MSG) or in a room (channel). Pictures are shared by uploading them to a temporary host like https://pomf.lain.la/ and then pasting the HTTP links. Code snippets or longer texts are shared by pasting them to a Pastebin like https://paste.opensuse.org/ and then sharing the HTTP link.
IRC does not have message history. You can only receive replies while your computer is turned on and connected to the channel you want to follow. Some people run their IRC programs on remote servers for that reason.
IRC is organised into networks. Each network consists of many servers. It (mostly) does not matter which server you connect to as long as it belongs to the network you want to use. Irssi supports connections to many networks at the same time.
Each network contains many channels, rooms that are often dedicated to discussing a specific topic. You can find many channels on https://netsplit.de/ or using a search engine with the keyword "IRC". Irssi supports joining many channels at the same time.
There is a rather large IRC network catering to free and open-source software and peer directed projects at https://libera.chat/ and a smaller one at https://www.oftc.net/ -- many free software projects still have support channels on these IRC networks (although some have moved to Matrix or proprietary platforms like Discord).
After (compiling and) installing Irssi, to start it, open a shell (Terminal) and type:
irssi
You should be greeted by a blinking cursor behind [(status)]. You are now in the status window of Irssi. Window is the Irssi name for what you might nowadays call a "Web browser tab".
If you're confused about what you are seeing on the Irssi screen, you can find an annotated screenshot of it at .
If you want, you can pick a nick name (handle) that will be shown to others reading your messages now, by typing
/set nick whatyouwant
Each command or message can be sent by pressing Enter. Commands in Irssi start with a /. If there is no /, then the line that you wrote will be sent as a message to the channel that you have open, for everyone to see.
Type /quit to get out of Irssi.
Irssi comes with some predefined networks. You can see the current list of networks by typing
/network
(the list will be shown in your status window)
To connect to one of the networks in the list, type /connect networkname, for example:
/connect liberachat
You should see several messages scroll by. After a while, you should be connected to the Libera Chat network.
:::{attention} Irssi version 1.2 or older may be lacking the liberachat network entry. See https://github.com/shabble/irssi-docs/wiki/liberachat for how to add it. :::
Many IRC networks (but not all) offer a way to register a user account. Sometimes (but not on all networks) the account registration also includes reserving a nick for you. How to register also differs by network. Some channels only allow users with registered accounts to join them, so it may be very important for you to register a user account.
User accounts are always specific to a network.
For the Libera Chat network, you can find instructions how to register and set up your account with Irssi on https://github.com/shabble/irssi-docs/wiki/liberachat#configure-sasl-automated-log-in
Once you are connected to a network, you can join channels by typing /join #channelname, for example:
/join #irssi
Now, a new window will open and you can send messages to the channel.
You can change between windows using the Ctrl+n or Ctrl+p keys, or--if your terminal is configured properly--using Alt+1, Alt+2, ... See for a list of all default key bindings.
By default, Irssi shows when someone joins or leaves a channel. These messages can waste a lot of lines and obscure the actual chat. To hide them, type
/window hidelevel +joins +parts +quits
To get them back
/window hidelevel -joins -parts -quits
If you want to hide them by default, /set window_default_hidelevel hidden joins parts quits
If you want to join a network that is not there, you first need to find at least one server of that network. Let's say you have found the room #hackint on netsplit.de and want to join it. Then you can find that the server is irc.hackint.org, port 6697, SSL (TLS) on. To add it to Irssi, use the commands:
/network add hackint
/server add -tls -network hackint irc.hackint.org 6697
Then, you can connect to the newly added network with
/connect hackint
If you are connected to multiple networks, you can change which one you are "talking" to (which one to send commands) by using the Ctrl+x key in the status window.
Most /commands have a help page, you can read it with
/help commandname
or on-line.
The settings that can be changed with /SET are described on -- the settingshelp script can be used to read it from within /help
You can enhance your Irssi by installing scripts. Many Perl scripts written by other Irssi users can be found on https://scripts.irssi.org/
Most of them should be compatible with Irssi 1.4 (but some may not, also see the Full Change log for some incompatible ones)