     [file docstyle.texi not included]
     [file emacsver.texi not included]

ERC
***

This manual is for ERC 5.6.0.30.1 as distributed with Emacs EMACSVER.

Copyright © 2005--2025 Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,'' and with the Back-Cover Texts as in (a) below.  A copy of the license is included in the section entitled ``GNU Free Documentation License''.

     (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and modify this GNU manual.''

     All Emacs Lisp code contained in this document may be used, distributed, and modified without restriction.

Introduction
************

ERC is a powerful, modular, and extensible IRC client for Emacs. It has been included in Emacs since 2006 (see History) and is also available on GNU ELPA.

IRC is short for Internet Relay Chat.  When using IRC, you can communicate with other users on the same IRC network.  There are many different networks---if you search for ``IRC networks'' in your favorite search engine, you will find up-to-date lists of IRC networks catering to various interests and topics.

To use IRC, you need an IRC client such as ERC.  Using the client, you connect to an IRC server.  Once you've done that, you will have access to all available channels on that server's network.  A channel is basically a chat room, and what you type in a channel will be shown to all other users in that channel.  You can be in several channels at the same time---ERC will show each channel in its own buffer.

IRC channel names always begin with a # character.  For example, the Emacs channel on Libera.Chat is #emacs, and the ERC channel is #erc.  Do not confuse them with the hashtags used on many social media platforms.

You can also send private messages to other IRC users on the same network, even if they are not in the same channels as you.

ERC comes with the following capabilities enabled by default.

  * Flood control

  * Timestamps

  * Join channels automatically

  * Buttonize URLs, nicknames, and other text

  * Wrap long lines

  * Highlight or remove IRC control characters

  * Highlight pals, fools, and other keywords

  * Detect netsplits

  * Complete nicknames and commands in a programmable fashion

  * Make displayed lines read-only

  * Input history

  * Track channel activity in the mode-line

Getting Started
***************

The command M-x erc will start ERC and prompt for the server to connect to.  If you're unsure of which server or network to connect to, we suggest starting with ``irc.libera.chat''.  There you will find the #emacs channels where you can chat with other Emacs users, and if you're having trouble with ERC, you can join the #erc channel and ask for help there.

At some point in your ERC journey, you'll inevitably want to change how the client looks and behaves.  As with other Emacs applications, the typical place to store your settings is your init.el.  If you would rather use the Customize interface, a good place to start is by running M-x customize-group RET erc RET.  In particular, ERC comes with lots of modules that may be enabled or disabled; to select which ones you want, do M-x customize-variable RET erc-modules RET.

Sample Session
==============

This example ERC session describes how to connect to the #emacs channel on Libera.Chat.  Also worth checking out is Libera's own introductory guide to IRC, https://libera.chat/guides/basics, which presents a more comprehensive overview without instructions specific to ERC.

  * Connect to Libera.Chat

     Run M-x erc RET.  Use irc.libera.chat for the server and 6667 for the port.  Choose a nickname, and hit y when asked if you'd prefer to connect over TLS.

  * Get used to the interface

     Switch to the Libera.Chat buffer if you're not already there. ERC calls this a server buffer, and it must exist for the duration of the session.  You will likely see some messages about ``ident'', authentication, and the like, followed by information describing the current server and the network.

  * Join the #emacs channel

     In the server buffer, type /join #emacs RET at the prompt. ERC will create a new buffer called #emacs.  If you've already configured ERC, you may need to switch to it manually.  Once there, you will see the channel's ``topic'' in the buffer's header line (see Header Lines (elisp)) and a list of people currently in the channel.  If you can't see the full topic, mouse over it or type /topic RET at the prompt.

  * Register your nickname with Libera.Chat

     In order to access essential network features, like speaking in certain channels and participating in private conversations, you'll likely have to ``register'' your nickname.  To do so, switch to the Libera.Chat buffer and type /msg NickServ register <password> <email> RET, replacing <password> and <email> with your desired account password and contact email (both sans quotes).  The server should tell you that the operation was successful.  See the official Libera.Chat docs if you encounter problems.

     In addition to creating an account, this process also ``authenticates'' you to the network's ``account services'' system for the duration of the session.  In other words, you're now logged in. However, when you connect in the future, you'll need to authenticate again by providing the same credentials somehow.  When you're finished with this walk through, see ``Next Steps'', below, to learn some ways to do that.

  * Talk to people in the channel

     Switch back to the #emacs buffer and type a message at the prompt, hitting RET once satisfied.  Everyone in the channel will now see your message.

  * Open a query buffer to talk to someone

     If you want to talk with someone in private, type /query <nick> RET, replacing <nick> with the their nickname.  As before, with the server buffer, if this new query buffer doesn't appear in the current window, you may have to switch to it.  Regardless, its name should match <nick>.  Once there, type something at the prompt and hit RET, and the other party will see it.

     Keep in mind that if either party isn't authenticated, you may not be able to converse at all.  Also, depending on the network, certain social conventions may apply to the practice of direct messaging.  As a general rule, queries should usually be reserved for personal matters rather than technical help, which can often benefit (and benefit from) a larger audience.

  * Next steps

     Try joining another channel, such as #erc, where ERC users and developers hang out (see Official IRC channels for more on the history of #emacs).  For ideas on various options to customize, see Sample Configuration.  To learn how ERC can authenticate you to the network automatically whenever you connect, see SASL.  As always, if you encounter problems, see Getting Help and Reporting Bugs.

Special Features
================

ERC has some features that distinguish it from some IRC clients.

  * multiple channels and multiple servers

     Every channel is put in a separate buffer.  Several IRC servers may be connected to at the same time.

  * private message separation

     Private conversations are treated as channels, and are put into separate buffers in Emacs.  We call these ``query buffers''.

  * highlighting

     Some occurrences of words can be highlighted, which makes it easier to track different kinds of conversations.

  * notification

     ERC can notify you that certain users are online.

  * channel tracking

     Channels can be hidden and conversation continue in the background.  You are notified when something is said in such a channel that is not currently visible.  This makes it easy to get Real Work done while still maintaining an IRC presence.

  * nick completion

     ERC can complete words upon hitting TAB, which eases the writing of nicknames in messages.

  * history

     Past actions are kept in history rings for future use.  To navigate a history ring, hit M-p to go backwards and M-n to go forwards.

  * multiple languages

     Different channels and servers may have different language encodings.

     multiple languages.  Please contact the Emacs developers if you are interested in helping with the translation effort.

  * user scripting

     Users can load scripts (e.g., auto greeting scripts) when ERC starts up.

     It is also possible to make custom IRC commands, if you know a little Emacs Lisp.  Just make an Emacs Lisp function and call it erc-cmd-NEWCOMMAND, where NEWCOMMAND is the name of the new command in capital letters.

  * auto reconnect

     If the connection goes away at some point, ERC will try to reconnect automatically.  If it fails to reconnect, and you want to try to manually reestablish the connection at some later point, switch to an ERC buffer and run the /RECONNECT command.

Keys Used in ERC
****************

This is a summary of keystrokes available in every ERC buffer.

C-a or <home> (erc-bol)
     Go to beginning of line or end of prompt.

RET (erc-send-current-line)
     Send the current line

TAB (completion-at-point or erc-button-next)
     If at prompt, complete the current word. Otherwise, move to the next link or button.

M-TAB (ispell-complete-word)
     Complete the given word, using ispell.

C-c C-a (erc-bol)
     Go to beginning of line or end of prompt.

C-c C-b (erc-switch-to-buffer)
     Use read-buffer to prompt for a ERC buffer to switch to.

C-c C-c (erc-toggle-interpret-controls)
     Toggle interpretation of control sequences in messages.

C-c C-d (erc-input-action)
     Interactively input a user action and send it to IRC.

C-c C-e (erc-toggle-ctcp-autoresponse)
     Toggle automatic CTCP replies (like VERSION and PING).

C-c C-f (erc-toggle-flood-control)
     Toggle use of flood control on sent messages.

C-c TAB (erc-invite-only-mode)
     Turn on the invite only mode (+i) for the current channel.

C-c C-j (erc-join-channel)
     Join channel.  If point is at the beginning of a channel name, use that as default.

C-c C-k (erc-go-to-log-matches-buffer)
     Interactively open an erc-log-matches buffer

C-c C-l (erc-save-buffer-in-logs)
     Append buffer contents to the log file, if logging is enabled.

C-c C-n (erc-channel-names)
     Run "/names #channel" in the current channel.

C-c C-o (erc-get-channel-mode-from-keypress)
     Read a key sequence and call the corresponding channel mode function. After doing C-c C-o, type in a channel mode letter.

     C-g means quit. RET lets you type more than one mode at a time. If l is pressed, erc-set-channel-limit gets called. If k is pressed, erc-set-channel-key gets called. Anything else will be sent to erc-toggle-channel-mode.

C-c C-p (erc-part-from-channel)
     Part from the current channel and prompt for a reason.

C-c C-q (erc-quit-server)
     Disconnect from current server after prompting for reason.

C-c C-r (erc-remove-text-properties-region)
     Clears the region (start,end) in object from all colors, etc.

C-c C-t (erc-set-topic)
     Prompt for a topic for the current channel.

C-c C-u (erc-kill-input)
     Kill current input line using erc-bol followed by kill-line.

Modules
*******

One way to add functionality to ERC is to customize which of its many modules are loaded.

You can do this by typing C-h v erc-modules RET and clicking customize near the bottom of the resulting help buffer, where it says ``You can customize this variable.''  When removing a module outside of Customize, you may wish to ensure it's disabled by invoking its associated minor-mode toggle with a nonpositive prefix argument, for example, C-u - M-x erc-spelling-mode RET.  Additionally, if you plan on loading third-party modules that perform atypical setup on activation, you may need to arrange for calling erc-update-modules in your init file.  Examples of such setup might include registering an erc-before-connect hook, advising erc-open, and modifying erc-modules itself.  On Emacs 29 and greater, you can also run erc-update-modules indirectly, via (setopt erc-modules erc-modules).

The following is a list of available modules.

autoaway
     Set away status automatically

autojoin
     Join channels automatically

bufbar
     List buffers belonging to a connection in a side window; part of Custom group erc-status-sidebar

button
     Buttonize URLs, nicknames, and other text

capab-identify
     Mark unidentified users on freenode and other servers supporting CAPAB.

command-indicator
     Echo command lines for ``slash commands'', like /JOIN #erc and /HELP join

completion (aka pcomplete)
     Complete nicknames and commands (programmable)

fill
     Wrap long lines

identd
     Launch an identd server on port 8113

irccontrols
     Highlight or remove IRC control characters

keep-place
     Remember your position in buffers

log
     Save buffers in logs

match
     Highlight pals, fools, and other keywords

menu
     Display a menu in ERC buffers

netsplit
     Detect netsplits

nicks
     Automatically colorize nicks

nickbar
     List participating nicks for the current target buffer in a side window; part of Custom group erc-speedbar

noncommands
     Don't display non-IRC commands after evaluation

notify
     Notify when the online status of certain users changes

notifications
     Send you a notification when you get a private message, or your nickname is mentioned

page
     Process CTCP PAGE requests from IRC

querypoll
     Update query participant data by continually polling the server

readonly
     Make displayed lines read-only

replace
     Replace text in messages

ring
     Enable an input history

sasl
     Enable SASL authentication

scrolltobottom
     Scroll to the bottom of the buffer

services
     Identify to Nickserv (IRC Services) automatically

smiley
     Convert smileys to pretty icons

sound
     Play sounds when you receive CTCP SOUND requests

spelling
     Check spelling of messages

stamp
     Add timestamps to messages

track
     Track channel activity in the mode-line

truncate
     Truncate buffers to a certain size

unmorse
     Translate morse code in messages

Auxiliary Modules
-----------------

For various reasons, the following modules aren't currently listed in the Custom interface for erc-modules, but feel free to add them explicitly.  They may be managed by another module or considered more useful when toggled interactively or just deemed experimental.

fill-wrap
     Wrap long lines using visual-line-mode

keep-place-indicator
     Remember your place in buffers with a visible reminder; activated interactively or via something like erc-join-hook

services-regain
     Automatically ask NickServ to reclaim your nick when reconnecting; experimental as of ERC 5.6

Required Modules
----------------

Note that some modules are essential to core IRC operations and thus not listed above.  You can nevertheless still remove these, but doing so demands special precautions to avoid degrading the user experience. At present, the only such module is networks, whose library ERC always loads anyway.

Local Modules
-------------

All modules operate as minor modes under the hood, and some newer ones may be defined as buffer-local.  These so-called ``local modules'' are a work in progress and their behavior and interface are subject to change.  As of ERC 5.5, the only practical differences are as follows:

 1. ``Control variables,'' like erc-sasl-mode, retain their values across IRC sessions and override erc-module membership when influencing module activation.

 2. Removing a local module from erc-modules via Customize not only disables its mode but also kills its control variable in all ERC buffers.

 3. ``Mode toggles,'' like erc-sasl-mode and the complementary erc-sasl-enable/erc-sasl-disable pairing, behave differently than their global counterparts.

In target buffers, a local module's activation state survives ``reassociation'' by default, but modules themselves always have the final say.  For example, a module may reset all instances of itself in its network context upon reconnecting.  Moreover, the value of a mode variable may be meaningless in buffers that its module has no interest in.  For example, the value of erc-sasl-mode doesn't matter in target buffers and may even remain non-nil after SASL has been disabled for the current connection (and vice versa).

When it comes to server buffers, a module's activation state only persists for sessions revived via the automatic reconnection mechanism or a manual /reconnect issued at the prompt.  In other words, this doesn't apply to sessions revived by an entry-point command, such as erc-tls, because such commands always ensure a clean slate by looking only to erc-modules.  Although a session revived in this manner may indeed harvest other information from a previous server buffer, it simply doesn't care which modules might have been active during that connection.

Lastly, a local mode's toggle command, like erc-sasl-mode, only affects the current buffer, but its ``non-mode'' cousins, like erc-sasl-enable and erc-sasl-disable, operate on all buffers belonging to their connection (when called interactively). And unlike global toggles, none of these ever mutates erc-modules.

Loading
-------

ERC loads internal modules in alphabetical order and third-party modules as they appear in erc-modules.  When defining your own module, take care to ensure ERC can find it.  An easy way to do that is by mimicking the example in the doc string for define-erc-module (also shown below).  For historical reasons, ERC falls back to requireing features.  For example, if some module my-module in erc-modules lacks a corresponding erc-my-module-mode command, ERC will attempt to load the library erc-my-module prior to connecting.  If this fails, ERC signals an error.  Users defining personal modules in an init file should (provide 'erc-my-module) somewhere to placate ERC. Dynamically generating modules on the fly is not supported.

Some older built-in modules have a second name along with a second minor-mode toggle, which is just a function alias for its primary counterpart.  For practical reasons, ERC does not define a corresponding variable alias because contending with indirect variables complicates bookkeeping tasks, such as persisting module state across IRC sessions.  New modules should definitely avoid defining aliases without a good reason.

Some packages have been known to autoload a module's definition instead of its minor-mode command, which severs the link between the library and the module.  This means that enabling the mode by invoking its command toggle isn't enough to load its defining library.  As such, packages should only supply module-related autoload cookies with an actual autoload form for their module's minor-mode command, like so:

     ;;;###autoload(autoload 'erc-my-module-mode "erc-my-module" nil t)
     (define-erc-module my-module nil
       "My doc string."
       ((add-hook 'erc-insert-post-hook #'erc-my-module-on-insert-post))
       ((remove-hook 'erc-insert-post-hook #'erc-my-module-on-insert-post)))

As implied earlier, packages can usually omit such cookies entirely so long as their module's prefixed name matches that of its defining library and the library's provided feature.

Finally, packages have also been observed to run erc-update-modules in top-level forms, forcing ERC to take special precautions to avoid recursive invocations.  Another unfortunate practice is mutating erc-modules itself upon loading erc, possibly by way of an autoload.  Doing this tricks Customize into displaying the widget for erc-modules incorrectly, with built-in modules moved from the predefined checklist to the user-provided free-form area.

Advanced Usage
**************

Connecting to an IRC Server
===========================

The easiest way to connect to an IRC server is to call M-x erc. If you want to assign this function to a keystroke, the following will help you figure out its parameters.

 -- Function: erc
     Select connection parameters and run ERC. Non-interactively, it takes the following keyword arguments.

       * SERVER

       * PORT

       * NICK

       * USER

       * PASSWORD

       * FULL-NAME

       * ID

     For example, calling the command like so

          (erc :server "irc.libera.chat" :full-name "J. Random Hacker")

     sets SERVER and FULL-NAME directly while leaving the rest up to functions like erc-compute-port.  Note that some arguments can't be specified interactively.  ID, in particular, is rarely needed (see Network Identifier).

To connect securely over an encrypted TLS connection, use M-x erc-tls.

 -- Function: erc-tls
     Select connection parameters and run ERC over TLS. Non-interactively, it takes the following keyword arguments.

       * SERVER

       * PORT

       * NICK

       * USER

       * PASSWORD

       * FULL-NAME

       * ID

       * CLIENT-CERTIFICATE

     That is, if called in the following manner

          (erc-tls :server "irc.libera.chat" :full-name "J. Random Hacker")

     the command will set SERVER and FULL-NAME accordingly, while helpers, like erc-compute-nick, will determine other parameters, and some, like client-certificate, will just be nil.

     To use a certificate with erc-tls, specify the optional CLIENT-CERTIFICATE keyword argument, whose value should be as described in the documentation of open-network-stream: if non-nil, it should either be a list where the first element is the file name of the private key corresponding to a client certificate and the second element is the file name of the client certificate itself to use when connecting over TLS, or t, which means that auth-source will be queried for the private key and the certificate.  Authenticating using a TLS client certificate is also referred to as ``CertFP'' (Certificate Fingerprint) authentication by various IRC networks.

     Examples of use:

          (erc-tls :server "irc.libera.chat" :port 6697
                   :client-certificate
                   '("/home/bandali/my-cert.key"
                     "/home/bandali/my-cert.crt"))

          (erc-tls :server "irc.libera.chat" :port 6697
                   :client-certificate
                   `(,(expand-file-name "~/cert-libera.key")
                     ,(expand-file-name "~/cert-libera.crt")))

          (erc-tls :server "irc.libera.chat" :port 6697
                   :client-certificate t)

     In the case of :client-certificate t, you will need to add a line like the following to your authinfo file (for example, ~/.authinfo.gpg):

          machine irc.libera.chat key /home/bandali/my-cert.key cert /home/bandali/my-cert.crt

     See Help for users (Emacs auth-source Library), for more on the .authinfo/.netrc backend of auth-source. For other uses of auth-source throughout ERC, see ERC's auth-source integration.

Server
------

 -- Function: erc-compute-server &optional server
     Return an IRC server name.

     This tries a progressively greater number of default methods until a non-nil value is found.

       * SERVER (the argument passed to this function)

       * The erc-server option

       * The value of the IRCSERVER environment variable

       * The erc-default-server variable

 -- User Option: erc-server
     IRC server to use if one is not provided.

Port
----

 -- Function: erc-compute-port &optional port
     Return a port for an IRC server.

     This tries a progressively greater number of default methods until a non-nil value is found.

       * PORT (the argument passed to this function)

       * The erc-port option

       * The erc-default-port variable

 -- User Option: erc-port
     IRC port to use if not specified.

     This can be either a string or a number.

Nick
----

 -- Function: erc-compute-nick &optional nick
     Return user's IRC nick.

     This tries a progressively greater number of default methods until a non-nil value is found.

       * NICK (the argument passed to this function)

       * The erc-nick option

       * The value of the IRCNICK environment variable

       * The result from the user-login-name function

 -- User Option: erc-nick
     Nickname to use if one is not provided.

     This can be either a string, or a list of strings. In the latter case, if the first nick in the list is already in use, other nicks are tried in the list order.

 -- User Option: erc-show-speaker-membership-status
     A boolean for including a channel member's status prefix in their display name when they speak.

 -- User Option: erc-nick-uniquifier
     The string to append to the nick if it is already in use.

 -- User Option: erc-try-new-nick-p
     If the nickname you chose isn't available, and this option is non-nil, ERC should automatically attempt to connect with another nickname.

     You can manually set another nickname with the /NICK command.

User
----

 -- Function: erc-compute-user &optional user
     Determine a suitable value to send as the first argument of the opening USER IRC command by consulting the following sources:

       * USER, the argument passed to this function

       * The option erc-email-userid, assuming erc-anonymous-login is non-nil

       * The result of calling the function user-login-name

 -- User Option: erc-email-userid
     A permanent username value to send for all connections.  It should be a string abiding by the rules of the network.

Password
--------

This parameter was traditionally meant to specify a server password to be sent along with the IRC PASS command.  However, such passwords aren't widely used.  Instead, networks typically expect them, when present, to convey other authentication information.  In the case of account-services (a.k.a., ``NickServ'') credentials, this typically involves a special syntax, such as myuser:mypass. IRC bouncers often do something similar but include a pre-configured network-ID component, for example, bncuser/mynet:bncpass.

In general, if you have not been asked by your network or bouncer to specify a repurposed server password, you should instead consider setting up services or, preferably, sasl, both ERC modules (see Modules).  In addition to performing network-account authentication, these obviate the need for this parameter completely, although both can optionally borrow it for their own purposes.  (see SASL in ERC.)

 -- User Option: erc-prompt-for-password
     If non-nil (the default), M-x erc and M-x erc-tls prompt for a server password.  This only affects interactive invocations of erc and erc-tls.

If you prefer, you can set this option to nil and use the auth-source facility to retrieve a server password, although hitting RET at the prompt may achieve the same effect. See ERC's auth-source integration, for more.

Full name
---------

 -- Function: erc-compute-full-name &optional full-name
     Return user's full name.

     This tries a progressively greater number of default methods until a non-nil value is found.

       * FULL-NAME (the argument passed to this function)

       * The erc-user-full-name option

       * The value of the IRCNAME environment variable

       * The result from the user-full-name function

 -- User Option: erc-user-full-name
     User full name.

     This can be either a string or a function to call.

ID
--

ERC uses an abstract designation, called network context identifier, for referring to a connection internally.  While normally derived from a combination of logical and physical connection parameters, an ID can also be explicitly provided via an entry-point command (like erc-tls).  Use this in rare situations where ERC would otherwise have trouble discerning between connections.

One such situation might arise when using multiple connections to the same network with the same nick but different (nonstandard) device identifiers, which some bouncers may support.  Another might be when mimicking the experience offered by popular standalone clients, which normally offer ``named'' persistent configurations with server buffers reflecting those names.  Yet another use case might involve third-party code needing to identify a connection unequivocally, but in a human-friendly way suitable for UI components.

When providing an ID as an entry-point argument, strings and symbols make the most sense, but any reasonably printable object is acceptable.

Authenticating via SASL
=======================

If you've used SASL elsewhere, you can probably skip to the examples below.  Otherwise, if you haven't already registered with your network, please do so now, referring to the network's own instructions for details.  If you're new to IRC and using a bouncer, know that you probably won't be needing this for the client-to-bouncer connection.

When you're ready to get started, add sasl to erc-modules, like you would any other module.  If unsure which mechanism to choose, stick with the default of PLAIN. Then try C-u M-x erc-tls RET, and give your account name for the user parameter and your account password for the server password.

 -- User Option: erc-sasl-mechanism
     The name of an SASL subprotocol type as a lowercase symbol. The value can be one of the following:

     plain or scram (``password-based'')
          Here, ``password'' refers to your account password, which is usually your NickServ password.  To make this work, customize erc-sasl-user and erc-sasl-password or specify the :user and :password keyword arguments when invoking erc-tls.

     external (via client TLS certificate)
          This works in conjunction with the :client-certificate keyword offered by erc-tls.  Just ensure you've registered your fingerprint with the network beforehand.  The fingerprint is usually a SHA1 or SHA256 digest in either "normalized" or "openssl" forms.  The first is lowercase without delims (deadbeef) and the second uppercase with colon seps (DE:AD:BE:EF).  These days, there's usually a CERT ADD command offered by NickServ that can register you automatically if you issue it while connected with a client cert.  See client-certificate.

          Additional considerations:

           1. Most IRCds will allow you to authenticate with a client cert but without the hassle of SASL (meaning you may not need this module).

           2. Technically, EXTERNAL merely indicates that an out-of-band mode of authentication is in effect (being deferred to), so depending on the specific application or service, there's a remote chance your server has something else in mind.

     ecdsa-nist256p-challenge
          This mechanism is quite complicated and currently requires the external openssl executable, so please use something else if at all possible.  Ignoring that, specify your key file (e.g., ~/pki/mykey.pem) as the value of erc-sasl-password, and then configure your network settings.  On servers running Atheme services, you can add your public key with NickServ like so:

               ERC> /msg NickServ set property \
                    pubkey AgGZmlYTUjJlea/BVz7yrjJ6gysiAPaQxzeUzTH4hd5j

          (You may be able to omit the property subcommand.)

 -- User Option: erc-sasl-user
     This should be your network account username, typically the same one registered with nickname services.  Specify this when your NickServ login differs from the :user you're connecting with. See username parameter.

 -- User Option: erc-sasl-password
     As noted elsewhere, the entry-point :password param was originally intended for traditional ``server passwords,'' but these aren't really used any more (see password parameter).  As such, this option defaults to borrowing that parameter for its own uses, thus allowing you to call erc-tls with :password set to your NickServ password.

     You can also set this to a nonemtpy string, and ERC will send that when needed, no questions asked.  Or, if you'd rather use auth-source, set erc-sasl-auth-source-function to a function, and ERC will perform an auth-source query instead.  In all cases, ERC will prompt you for input as a last resort.

     Lastly, if your mechanism is ecdsa-nist256p-challenge, this option should instead hold the file name of your key.

 -- User Option: erc-sasl-auth-source-function
     This is nearly identical to the other ERC auth-source function options (see auth-source functions) except that the default value here is nil, meaning you have to set it to something like erc-auth-source-search for queries to be performed.  For convenience, this module provides the following as a possible value:

      -- Function: erc-sasl-auth-source-password-as-host &rest plist
          Setting erc-sasl-auth-source-function to this function tells ERC to use erc-sasl-password for the :host field when querying auth-source, even if its value is the default :password, in which case ERC knows to ``resolve'' it to erc-session-password and use that as long as it's non-nil.  Otherwise, ERC just defers to erc-auth-source-search to determine the :host, along with everything else.

     As long as this option specifies a function, ERC will pass it the ``resolved'' value of erc-sasl-user for the auth-source :user param.

 -- User Option: erc-sasl-authzid
     In the rarest of circumstances, a network may want you to specify a specific role or assume an alternate identity.  In most cases, this happens because the server is buggy or misconfigured.  If you suspect such a thing, please contact your network operator.  Otherwise, just leave this set to nil.

Examples
--------

  * Defaults

          (erc-tls :server "irc.libera.chat" :port 6697
                   :nick "aph"
                   :user "APHacker"
                   :password "changeme")

     Here, after adding sasl to erc-modules via the Customize interface, you authenticate to Libera.Chat using the PLAIN mechanism and your NickServ credentials, APHacker and changeme.

  * External

          (setopt erc-sasl-mechanism 'external)

          (erc-tls :server "irc.libera.chat" :port 6697 :nick "aph"
                   :client-certificate
                   '("/home/aph/my.key" "/home/aph/my.crt"))

     You decide to switch things up and try out the EXTERNAL mechanism.  You follow your network's instructions for telling NickServ about your client-certificate's fingerprint, and you authenticate successfully.

  * Multiple networks

          # ~/.authinfo.gpg

          machine irc.libera.chat key /home/aph/my.key cert /home/aph/my.crt
          machine Example.Net login alyssa password sEcReT
          machine Example.Net login aph-bot password sesame

          ;; init.el

          (defun my-erc-up (network)
            (interactive "Snetwork: ")
            (require 'erc-sasl)
            (or (let ((erc-modules (cons 'sasl erc-modules)))
                  (pcase network
                    ('libera
                     (let ((erc-sasl-mechanism 'external))
                       (erc-tls :server "irc.libera.chat"
                                :client-certificate t)))
                    ('example
                     (let ((erc-sasl-auth-source-function
                            #'erc-sasl-auth-source-password-as-host))
                       (erc-tls :server "irc.example.net"
                                :user "alyssa"
                                :password "Example.Net")))))
                ;; Non-SASL
                (call-interactively #'erc-tls)))

     You've started storing your credentials with auth-source and have decided to try SASL on another network as well.  But there's a catch: this network doesn't support EXTERNAL.  You use let-binding to work around this and successfully authenticate to both networks.  (Note that this example assumes you've removed sasl from erc-modules globally and have instead opted to add it locally when connecting to preconfigured networks.)

Troubleshooting
---------------

First and foremost, please know that ERC's SASL offering is currently limited by a lack of support for proper IRCv3 capability negotiation. In most cases, this shouldn't affect your ability to authenticate.

If you're struggling, remember that your SASL password is almost always your NickServ password.  When in doubt, try restoring all SASL options to their defaults and calling erc-tls with :user set to your NickServ account name and :password to your NickServ password.  If you're still having trouble, please contact us (see Getting Help and Reporting Bugs).

As you try out different settings, keep in mind that it's best to create a fresh session for every change, for example, by calling erc-tls from scratch.  More experienced users may be able to get away with cycling erc-sasl-mode and issuing a /reconnect, but that's generally not recommended.  Whatever the case, you'll probably want to temporarily disable erc-server-auto-reconnect while experimenting.

Sample Configuration
====================

Here is an example configuration for ERC.  Don't panic if you aren't familiar with use-package or have no interest in learning it.  For our purposes, it's just a means of presenting configuration details in a tidy, standardized format.  If it helps, just pretend it's some make-believe, pseudo configuration language. And while the syntax below is easy enough to intuit and adapt to your setup, you may wish to keep the following in mind:

  * Each use-package ``declaration'' focuses on a library ``feature'', which is just a symbol you'd normally require in your config.

  * Emacs loads anything in a :config section after loading whatever library provides the declaration's feature.

  * Everything in a :custom or :custom-face section is basically something you'd find in your custom-file.

  * For more info, see Named Features (elisp), or see use-package.

The following would typically go in your init file.  Experienced users may opt to keep any non-settings, like commands and functions, in a dedicated ~/.emacs.d/.ercrc.el.  Whatever the case, please keep in mind that you can replace nearly all of the following with Custom settings (see Sample configuration via Customize).

     ;;; My ERC configuration -*- lexical-binding: t -*-

     (use-package erc
       :config
       ;; Prefer SASL to NickServ, colorize nicknames, and show side panels
       ;; with joined channels and members
       (setopt erc-modules
               (seq-union '(sasl nicks bufbar nickbar scrolltobottom)
                          erc-modules))

       :custom
       ;; Protect me from accidentally sending excess lines.
       (erc-inhibit-multiline-input t)
       (erc-send-whitespace-lines t)
       (erc-ask-about-multiline-input t)
       ;; Scroll all windows to prompt when submitting input.
       (erc-scrolltobottom-all t)

       ;; Reconnect automatically using a fancy strategy.
       (erc-server-reconnect-function #'erc-server-delayed-check-reconnect)
       (erc-server-reconnect-timeout 30)

       ;; Show new buffers in the current window instead of a split.
       (erc-interactive-display 'buffer)

       ;; Insert a newline when I hit <RET> at the prompt, and prefer
       ;; something more deliberate for actually sending messages.
       :bind (:map erc-mode-map
                   ("RET" . nil)
                   ("C-c C-c" . #'erc-send-current-line))

       ;; Emphasize buttonized text in notices.
       :custom-face (erc-notice-face ((t (:slant italic :weight unspecified)))))

     (use-package erc-sasl
       ;; Since my account name is the same as my nick, free me from having
       ;; to hit C-u before M-x erc to trigger a username prompt.
       :custom (erc-sasl-user :nick))

     (use-package erc-join
       ;; Join #emacs and #erc whenever I connect to Libera.Chat.
       :custom (erc-autojoin-channels-alist '((Libera.Chat "#emacs" "#erc"))))

     (use-package erc-fill
       :custom
       ;; Prefer one message per line without continuation indicators.
       (erc-fill-function #'erc-fill-wrap)
       (erc-fill-static-center 18)

       :bind (:map erc-fill-wrap-mode-map ("C-c =" . #'erc-fill-wrap-nudge)))

     (use-package erc-track
       ;; Prevent JOINs and PARTs from lighting up the mode-line.
       :config (setopt erc-track-faces-priority-list
                       (remq 'erc-notice-face erc-track-faces-priority-list))

       :custom (erc-track-priority-faces-only 'all))

     (use-package erc-goodies
       ;; Turn on read indicators when joining channels.
       :hook (erc-join . my-erc-enable-keep-place-indicator-on-join))

     (defvar my-erc-read-indicator-channels '("#emacs")
       "Channels in which to show a `keep-place-indicator'.")

     (defun my-erc-enable-keep-place-indicator-on-join ()
       "Enable read indicators for certain queries or channels."
       (when (member (erc-default-target) my-erc-read-indicator-channels)
         (erc-keep-place-indicator-mode +1)))

     ;; Handy commands from the Emacs Wiki.
     (defun erc-cmd-TRACK (&optional target)
       "Start tracking TARGET or that of current buffer."
       (setq erc-track-exclude
             (delete (or target (erc-default-target) (current-buffer))
                     erc-track-exclude)))

     (defun erc-cmd-UNTRACK (&optional target)
       "Stop tracking TARGET or that of current buffer."
       (setq erc-track-exclude
             (cl-pushnew (or target (erc-default-target) (current-buffer))
                         erc-track-exclude
                         :test #'equal)))

Those familiar with use-package may have noticed the lack of :defer keyword args.  This was done to conserve space, but you can just pretend that this user has enabled use-package-always-defer elsewhere.

Via Customize
-------------

As mentioned, Customize users can accomplish nearly all of the above via the Customize interface.  Start by running M-x customize-group RET erc RET, and search for ``Modules'' with C-s modules RET.  Toggle open the flyout menu to reveal the full widget panel, a web-form-like interface for ``Erc Modules''.  Tick the boxes for bufbar, nickbar, nicks, sasl, and scrolltobottom.

Next, search for the phrases ``Erc Ask About Multiline Input'', ``Erc Inhibit Multiline Input'', and ``Erc Send Whitespace Lines''.  These are the print names of three boolean options that control how ERC treats prompt input containing line breaks.  When visiting each option's section, twirl open its triangle icon to reveal its widget UI, and click its [Toggle] button to set its value to t. While going about this, you may find it helpful to glance at the descriptions just in case you want to disable them later.  When finished, hit C-x C-s or click [Apply and Save] atop the buffer.

Now do the same for another couple options, this time having to do with automatic reconnection.  But instead of searching for their print names, try running M-x customize-option RET <option> RET, replacing <option> with:

  * erc-server-reconnect-function, a function

  * erc-server-reconnect-timeout, a number

(If it helps, hit TAB for completion.)  As you may have noticed, when customizing options individually, each buffer displays but a single option's widget.  When you get to the buffer for ``Erc Server Reconnect Function'', you'll see that [Toggle] has been replaced with [Value Menu] and that clicking it reveals three choices in a pop-up window.  Enter 1 to select erc-server-delayed-check-reconnect before TAB'ing over to [State] and hitting RET.  Enter 1 again, this time to persists your changes.

For the final option, erc-server-reconnect-timeout, you'll encounter a text field (instead of a button), which works like those in a typical web form.  Enter 30 and hit C-x C-s to save. Just for fun, click the group link for Erc Server at the bottom of the buffer.  You could just as well have set the last two options from this ``custom group'' buffer alone, which very much resembles the one for the Erc group, which is actually the ``parent'' of this group (note the ``breadcrumb'' for group Erc atop the buffer). Indeed, you can always get back here by running M-x customize-group RET erc-server RET from almost anywhere in Emacs.

To make sure you've got this, try quickly customizing the option erc-interactive-display, which lives in the Erc Buffers group (M-x customize-group RET erc-buffers RET).  As its doc string explains, the option controls where new buffers show up when you do M-x erc-tls RET or issue certain slash commands, like /JOIN #emacs-beginners RET, at ERC's prompt.  Change its value to the symbol buffer by choosing Use current window (item 5) from the option's [Value Menu].  Don't forget to save.

If you need more practice, try enabling the boolean option erc-scrolltobottom-all, which lives in the Erc Display group (M-x customize-group RET erc-display RET). When enabled, this option tells the scrolltobottom module to adjust all ERC windows instead of just the one you're currently typing in.

Now it's time to set some key bindings for erc-mode-map, a major-mode keymap active in all ERC buffers.  In general, it's best to do this part either entirely or in conjunction with some lisp code in you init file.  However, to keep things ``simple'', we'll do it all in customization buffers.  To get started, hit M-x customize-group RET erc-hooks RET and search for ``Erc Mode Hook''.  In the widget form, click [INS], and paste the following into the value field in place of the default text.

     (lambda ()
       (keymap-set erc-mode-map "RET" nil)
       (keymap-set erc-mode-map "C-c C-c" 'erc-send-current-line))

Don't worry about the line breaks.  Emacs is smart enough to handle those.  When you're ready, click [Apply and Save].

Next, try tweaking the face ERC uses to stylize server messages that say things like ``SoAndSo has joined channel #chan''.  Type M-x customize-face RET erc-notice-face RET.  Click the ``link''-looking button at the very bottom that says something like ``Show All Attributes''.  Untick Weight and tick Slant. Then, in the latter's [Value Menu], enter 0 for italic.  Hit C-x C-s to save.

Time for some more involved configuring.  From now on, if something isn't applicable to your setup, just skip ahead.  Also, note that if you've installed ERC from GNU ELPA, you may need to load libraries for groups and options you'd like to customize before Emacs can create a customization buffer.  For example, to do this for the group erc-sasl, run M-: (require 'erc-sasl) RET.

Speaking of SASL, those already authenticating with it may have noticed that connecting interactively requires running C-u M-x erc-tls RET in order to receive a ``User'' prompt for your account name.  However, if your nickname happens to be the same as your account name, you can avoid the leading C-u by customizing the option erc-sasl-user to the keyword symbol :nick. At the time of writing, you'd hit 2 when prompted by the option's [Value menu].  Hit C-x C-s to save your changes.

One of ERC's most configured options lives in erc-join, and it determines the channels you join upon connecting.  To make it work for you, customize the option erc-autojoin-channels-alist.  In the customization widget, hit [INS] to create a new entry.  In the Network: field, type Libera.Chat.  Under Channels:, hit [INS] again, this time to create a field to enter a channel name, and enter #emacs.  Now, find and click on the lowermost [INS], and this time enter #erc in the Name: field.  Save your changes.

If you're new to ERC, you may not be familiar with the various ways it can ``fill'' message text by inserting line breaks.  The most modern fill style is called fill-wrap, and it's available by customizing erc-fill-function to erc-fill-wrap, which appears as Dynamic word-wrap in the option's [Value Menu].  After setting this, change the related option erc-fill-static-center to the integer 18.  Save your changes.  As a bonus exercise, try binding the key C-c = to the function erc-fill-wrap-nudge in the minor-mode keymap erc-fill-wrap-mode-map (hint: the minor mode's hook is called erc-fill-wrap-mode-hook, and it's not a member of any customization group).

ERC users tend to be picky about the mode line.  If you find that you'd rather not see changes when people join and leave channels, customize the option erc-track-faces-priority-list.  When visiting its customization buffer, you'll notice it's quite busy. Ignore everything and type C-s erc-notice-face RET.  Click the [DEL] button at the beginning of the line you end up on, and save your changes.  Next, customize the related option erc-track-priority-faces-only to the [Value Menu] choice all.  Once again, save your changes.

Let's say you'd like to enable a local module (ERC's version of a local minor mode) in a specific channel.  One way to do that is by running some code to activate the module if the channel's name matches.  Try that now by customizing the option erc-join-hook. Add the following in the value field before saving your changes:

     (lambda ()
       (require 'erc-goodies)
       (when (equal (erc-default-target) "#emacs")
         (erc-keep-place-indicator-mode +1)))

Lastly, if you really want the two slash commands defined at the end of the previous section, you can put them in any file listed in erc-startup-file-list, such as ~/.emacs.d/.ercrc.el. Make sure to put (require 'erc-track) near the top of the file. These will allow you to type /TRACK RET and /UNTRACK RET in channels and query buffers to tell ERC whether to show activity from these buffers in the mode line.

Integrations
============

URL
---

For anything to work, you'll want to set url-irc-function to url-irc-erc.  As a rule of thumb, libraries relying directly on url-retrieve should be fine out the box from Emacs 29.1 onward. On older versions of Emacs, you may need to (require 'erc) beforehand.  See Retrieving URLs (URL).

For other apps and libraries, such as those relying on the higher-level browse-url, you'll oftentimes be asked to specify a pattern, sometimes paired with a function that accepts a string URL as a first argument.  For example, with EWW, you may need to tack something like "\\|\\`irc6?s?:" onto the end of eww-use-browse-url.  But with gnus-button-alist, you'll need a function as well:

       '("\\birc6?s?://[][a-z0-9.,@_:+%?&/#-]+" 0 t browse-url-irc 0)

Users on Emacs 28 and below may need to use browse-url instead.

SOCKS
-----

People wanting to connect to IRC through a SOCKS proxy are most likely interested in doing so over TOR (The Onion Router).  If that's not you, please adapt these instructions accordingly.  Otherwise, keep in mind that support for Tor is experimental and thus insufficient for safeguarding a user's identity and location, especially in the case of targeted individuals.

ERC's preferred Tor setup works by accessing a local Tor service through the built-in socks.el library that ships with Emacs. Other means of accessing Tor, such as via torsocks, are not supported.  Before getting started, check that your Tor service is up and running.  You can do that with the following command:

     curl --proxy socks5h://localhost:9050 https://check.torproject.org | \
       grep 'Congratulations'

Networks and servers differ in how they expose Tor endpoints.  In all cases, you'll want to first set the option socks-server to something appropriate, like ("tor" "127.0.0.1" 9050 5).  For some networks, setting erc-server-connect-function to socks-open-network-stream might be enough.  Others, like Libera.Chat, involve additional setup.  At the time of writing, connecting to that network requires both TLS and a permitted SASL mechanism, like EXTERNAL (see SASL), as shown in the following example:

     (require 'erc)
     (require 'socks)

     (defun my-erc-open-socks-tls-stream (&rest args)
       (let ((socks-username "")
             (socks-password "")
             (socks-server '("tor" "localhost" 9050 5)))
         (apply #'erc-open-socks-tls-stream args)))

     (let* ((erc-modules (cons 'sasl erc-modules))
            (erc-sasl-mechanism 'external)
            (erc-server-connect-function #'my-erc-open-socks-tls-stream))
       (erc-tls
        :server "libera75jm6of4wxpxt4aynol3xjmbtxgfyjpu34ss4d7r7q2v5zrpyd.onion"
        :port 6697
        :nick "jrh"
        :user "jrandomhacker"
        :full-name "J. Random Hacker"
        :client-certificate (list "/home/jrh/key.pem" "/home/jrh/cert.pem")))

Here, the user-provided my-erc-open-socks-tls-stream ensures that the preferred values for socks-server and friends will be available when reconnecting.  If you plan on using SOCKS with ERC exclusively, you can just set those options and variables globally and bind erc-server-connect-function to erc-open-socks-tls-stream instead.

auth-source
-----------

You can configure ERC to use the built-in auth-source library for looking up passwords. See auth-source (Emacs auth-source Library), for general info on setting up various backends, but keep in mind that some of these may not be compatible.  Those currently supported are netrc, plstore, json, secrets, and pass.  To get started with the default backend, netrc, put a line like the following in your ~/.authinfo.gpg (or any file named in the option auth-sources):

     machine irc.example.net login mynick password sEcReT

Server Passwords
................

When retrieving passwords to accompany the IRC PASS command (see password parameter), ERC asks auth-source to match the SERVER parameter of erc-tls against each entry's host field (machine irc.example.net in the above example).  Unfortunately, specifying a network, like Libera.Chat, or a specific network server, like platinum.libera.chat, won't normally work for looking up a server password because that information isn't available during opening introductions.  (Actually, ERC can find entries with arbitrary host values for any context, including server passwords, but that requires customizing the more advanced options below.)

If ERC can't find a suitable server password, it will just skip the IRC PASS command altogether, something users may want when using CertFP or engaging NickServ via ERC's services module. If that appeals to you, consider customizing the option erc-auth-source-server-function to nil to skip server-password lookup for all servers.  Note that some networks and IRCds may accept account-services authentication via server password. Also, some ERC modules may commandeer the erc-tls PASSWORD parameter for their own ends, which likely don't involve a server password.

The services module
...................

You can use auth-source to authenticate to account services the traditional way through a bot called NickServ.  To do so, add services to erc-modules and set the option erc-use-auth-source-for-nickserv-password to t.  After that, expect the user parameter in relevant auth-source queries to be your current nickname.

Most of the time, a query's precise contextual details (such as whether a nick was granted or forcibly assigned) shouldn't affect how you define entries in your backend.  However, if something isn't quite working, you may want to investigate the interplay between the option erc-nickserv-identify-mode and account services.  In particular, if you find yourself facing nicks suffixed with an erc-nick-uniquifier (the infamous `), check that the network's entry in erc-nickserv-alist is up to date, and do let us know if something's off (see Getting Help and Reporting Bugs). Of course, if you've had your fill of fiddling with this module, consider switching to SASL for what's likely a more consistent auth-source experience.  (see SASL.)

Default query behavior
......................

When preparing entries for your backend, it may help to get a feel for how ERC and its modules conduct searches, especially when exploring a new context, such as channel keys.  Overall, though, ERC tries to be consistent in performing queries across various authentication contexts.  Here's what to expect with respect to the host field, which, by default, most heavily influences the fate of a query:

 1. entries featuring custom identifiers and networks are matched first (see Network Identifier)

 2. followed by network-specific servers

 3. and, finally, dialed endpoints (typically the SERVER argument passed to erc-tls)

The following netrc-style entries appear in order of precedence:

     machine Libera/cellphone login MyNick password sEcReT
     machine Libera.Chat login MyNick password sEcReT
     machine zirconium.libera.chat login MyNick password sEcReT
     machine irc.libera.chat login MyNick password sEcReT

Remember that field labels vary per backend, so machine (in netrc's case) maps to auth-source's generalized notion of a host, hence the :host keyword parameter to auth-source-search. Also, be sure to mind the syntax of your chosen backend medium.  For example, always quote channel names in a netrc file.

Lastly, if this all seems overly nuanced or just plain doesn't appeal to you, please see options erc-auth-source-services-function and friends, described just below.

Custom query functions
......................

These let you query auth-source your way.  Most users can simply ignore the passed-in arguments and get by with something like the following:

     (defun my-fancy-auth-source-func (&rest _)
       (let* ((host (read-string "host: " nil nil "default"))
              (pass (auth-source-pick-first-password :host host)))
         (if (and pass (string-search "libera" host))
             (concat "MyNick:" pass)
           pass)))

 -- User Option: erc-auth-source-server-function

 -- User Option: erc-auth-source-services-function

 -- User Option: erc-auth-source-join-function

     ERC calls these functions with keyword arguments recognized by auth-source-search, namely, those deemed most relevant to the current context, if any.  For example, when identifying to services, :user contains your current nickname.  Generalized parameter names, like :user and :host, are always preferred over backend specific ones, like :login or :machine.  In return, ERC expects a string if the search succeeds or nil if it fails.

     The default value for all three options is the function erc-auth-source-search.  It tries to merge relevant contextual parameters with those provided or discovered from the logical connection or the underlying transport.

     For using auth-source along with SASL, see SASL auth-source function.

Channel keys
............

ERC also consults auth-source to find ``keys'' that may be required by certain channels you join.  When modifying a traditional auth-source entry for this purpose, put the channel name in the user field (for example, login "#fsf", in netrc's case). The actual key goes in the password (or secret) field.

Troubleshooting
---------------

By default, ERC queries auth-source for channel keys and server passwords (see auth-source Server Password), as well as other, module-specific credentials.  In general, if you're having trouble calling auth-source-search in a custom query function, like erc-auth-source-server-function, try temporarily setting the variable auth-source-debug to t and checking *Messages* periodically for insights into how auth-source is operating.

If you're using a GPG-encrypted file and find that customizing one of the function-valued query options doesn't solve your problem, explore options epg-pinentry-mode and epg-debug in the epg Custom group (see GnuPG Pinentry (EasyPG Assistant)).  Additionally, keep an eye out for an *Error* buffer, which may contain more specific clues about your situation.  If you use the libsecrets integration (see Secret Service API (Emacs auth-source)) with something like GNOME Keyring, you may need to check the ``remember'' box in the passphrase popup dialog to avoid being prompted for confirmation every time you run ERC.  If it doesn't work at first, try logging out.  And when in doubt, try using the Emacs command secrets-show-secrets to browse the Login keyring.  There should be a GnuPG/stored-by entry with a value of GnuPG Pinentry or similar.

display-buffer
--------------

ERC supports the ``action'' interface used by display-buffer and friends from window.el.  See Displaying Buffers (Emacs Lisp), for specifics.  When ERC displays a new or ``reassociated'' buffer, it consults its various buffer-display options, such as erc-buffer-display, to decide whether and how the buffer ought to appear in a window.  Exactly which one it consults depends on the context in which the buffer is being manifested.

For some buffer-display options, the context is pretty cut and dry. For instance, in the case of erc-receive-query-display, you're receiving a query from someone you haven't yet chatted with in the current session.  For other options, like erc-interactive-display, the precise context varies.  For example, you might be opening a query buffer with the command /QUERY bob RET or joining a new channel with /JOIN #chan RET.  Power users wishing to distinguish between such nuanced contexts or just exercise more control over buffer-display behavior generally can elect to override these options by setting one or more to a ``display-buffer-like'' function that accepts a BUFFER and an ACTION argument.

Examples
........

In this first example, a user-provided buffer-display function displays new server buffers in the current window when issuing an M-x erc-tls RET and in a split window for all other interactve contexts covered by the option erc-interactive-display, like clicking an irc://-style URL (see URL).

     (defun my-erc-interactive-display-buffer (buffer action)
       "Pop to BUFFER when running \\[erc-tls], clicking a link, etc."
       (when-let ((alist (cdr action))
                  (found (alist-get 'erc-interactive-display alist)))
         (if (eq found 'erc-tls)
             (pop-to-buffer-same-window buffer action)
           (pop-to-buffer buffer action))))

     (setopt erc-interactive-display #'my-erc-interactive-display-buffer)

Observe that ERC supplies the names of buffer-display options as ACTION alist keys and pairs them with contextual constants, like the symbols erc-tls or url, the full lineup of which are listed below.

In this second example, for Emacs 29 and above, the user writes three predicates that somewhat resemble the ``display-buffer-like'' function above.  These too look for ACTION alist keys sharing the names of ERC's buffer-display options (and, in one case, a module's minor mode).

     (defun my-erc-disp-entry-p (_ action)
       (memq (cdr (or (assq 'erc-buffer-display action)
                      (assq 'erc-interactive-display action)))
             '(erc-tls url)))

     (defun my-erc-disp-query-p (_ action)
       (or (eq (cdr (assq 'erc-interactive-display action)) '/QUERY)
           (and (eq (cdr (assq 'erc-receive-query-display action)) 'PRIVMSG)
                (member (erc-default-target) '("bob" "alice")))))

     (defun my-erc-disp-chan-p (_ action)
       (or (assq 'erc-autojoin-mode action)
           (and (eq (cdr (assq 'erc-buffer-display action)) 'JOIN)
                (member (erc-default-target) '("#emacs" "#fsf")))))

You'll notice we ignore the BUFFER parameter of these predicates because ERC ensures that BUFFER is already current (which is why we can freely call erc-default-target).  Note also that we cheat a little by treating the ACTION parameter like an alist when it's really a cons of one or more functions and an alist.

To complement our predicates, we set all three buffer-display options referenced in their ACTION-alist lookups to display-buffer.  This tells ERC to defer to that function in the display contexts covered by these options.

     (setopt erc-buffer-display #'display-buffer
             erc-interactive-display #'display-buffer
             erc-receive-query-display #'display-buffer
             ;;
             erc-auto-reconnect-display 'bury)

The last option above just tells ERC to avoid any buffer-display machinery when auto-reconnecting.  (For historical reasons, ERC's buffer-display options use the term ``bury'' to mean ``ignore'' rather than bury-buffer.)

Finally, we compose our predicates into buffer-match-p conditions and pair them with various well known display-buffer action functions and action-alist members.

     (setopt display-buffer-alist

             ;; Create new frame with M-x erc-tls RET or (erc-tls ...)
             '(((and (major-mode . erc-mode) my-erc-disp-entry-p)
                display-buffer-pop-up-frame
                (reusable-frames . visible))

               ;; Show important chans and queries in a split.
               ((and (major-mode . erc-mode)
                     (or my-erc-disp-chan-p my-erc-disp-query-p))
                display-buffer-pop-up-window)

               ;; Ignore everything else.
               ((major-mode . erc-mode)
                display-buffer-no-window
                (allow-no-window . t))))

Of course, we could just as well set our buffer-display options to one or more homespun functions instead of bothering with display-buffer-alist at all (in what would make for a more complicated version of our first example).  But perhaps we already have a growing menagerie of similar predicates and like to keep everything in one place in our init.el.

Action alist items
..................

Option-based keys:
     All keys are symbols, as are values, unless otherwise noted.

       * erc-buffer-display

            - JOIN

            - NOTICE

            - PRIVMSG

            - erc (entry point called non-interactively)

            - erc-tls

       * erc-interactive-display

            - /QUERY

            - /JOIN

            - /RECONNECT

            - url (hyperlink clicked)

            - erc (entry point called interactively)

            - erc-tls

       * erc-receive-query-display

            - NOTICE

            - PRIVMSG

       * erc-auto-reconnect-display

            - something non-nil

Module-based (minor-mode) keys:

       * erc-autojoin-mode

            - channel name as a string, e.g., "#chan"

Options
=======

This section is extremely incomplete.  For now, the easiest way to check out all the available options for ERC is to do M-x customize-group RET erc RET.

 -- User Option: erc-hide-list
     If non, nil, this is a list of IRC message types to hide, e.g.:

          (setq erc-hide-list '("JOIN" "PART" "QUIT"))

 -- User Option: erc-network-hide-list
     If non, nil, this is a list of IRC networks and message types to hide, e.g.:

          (setq erc-network-hide-list (("Libera.Chat" "JOIN" "PART" "QUIT")
          ("OFTC" "JOIN" "PART""))

 -- User Option: erc-channel-hide-list
     If non, nil, this is a list of IRC channels and message types to hide, e.g.:

          (setq erc-channel-hide-list (("#erc" "JOIN" "PART" "QUIT")
          ("#emacs" "NICK"))

 -- User Option: erc-lurker-hide-list
     Like erc-hide-list, but only applies to messages sent by lurkers.  The function erc-lurker-p determines whether a given nickname is considered a lurker.

Getting Help and Reporting Bugs
*******************************

After you have read this guide, if you still have questions about ERC, or if you have bugs to report, there are several places you can go.

  * https://www.emacswiki.org/emacs/ERC is the emacswiki.org page for ERC.  Anyone may add tips, hints, etc. to it. If you do so, please help keep it up to date.

  * You can ask questions about using ERC on the Emacs mailing list, https://lists.gnu.org/mailman/listinfo/help-gnu-emacs, as well as on ERC's own low-volume list, https://lists.gnu.org/mailman/listinfo/emacs-erc.

  * You can visit the IRC Libera.Chat channel #emacs.  Many of the contributors are frequently around and willing to answer your questions.  You can also try the relatively quiet #erc, on the same network, for more involved questions.

  * You can check GNU ELPA between Emacs releases to see if a newer version is available that might contain a fix for your issue: https://elpa.gnu.org/packages/erc.html.

     To upgrade, run M-x list-packages RET.  In the *Packages* (package-menu-mode) buffer, click the erc package link for the desired version.  If unsure, or if the version column is too narrow to tell, try the bottom-most candidate. In the resulting help-mode buffer, confirm the version and click Install.  Make sure to restart Emacs before reconnecting to IRC, and don't forget that you can roll back to the previous version by running M-x package-delete RET. See Packages (The Emacs Editor), for more information.

     Note that a bug affecting Emacs's packaging machinery may prevent the above method from working on Emacs versions 29 and below.  Users on 29 can try running C-u M-x package-install RET instead. Users on 28 and below can click on the installed erc line item in the *Packages* buffer instead of the newest one, and then, in the resulting help-mode buffer, find and activate the button for the newest version, which should appear in the summary item Other versions.

     In the rare instance you need an emergency fix or have volunteered to test an edge feature between ERC releases, you can try adding ("devel" . "https://elpa.gnu.org/devel/") to package-archives prior to performing the steps above.  For this, you'll want to instead select a snapshot version from the menu.  Please be aware that when going this route, the latest changes may not yet be available and you run the risk of incurring other bugs and encountering unstable features.

  * To report a bug in ERC, use M-x erc-bug.

History
*******

ERC was originally written by Alexander L. Belikoff and Sergey Berezin. They stopped development around December 1999.  Their last released version was ERC 2.0.

P.S.: If one of the original developers of ERC reads this, we'd like to receive additional information for this file and hear comments in general.

  * 2001

     In June 2001, Mario Lang and Alex Schroeder took over development and created a ERC Project at https://sourceforge.net/projects/erc.

     In reaction to a mail about the new ERC development effort, Sergey Berezin said, ``First of all, I'm glad that my version of ERC is being used out there.  The thing is, I do not have free time and enough incentive anymore to work on ERC, so I would be happy if you guys take over the project entirely.''

     So we happily hacked away on ERC, and soon after (September 2001) released the next "stable" version, 2.1.

     Most of the development of the new ERC happened on #emacs on irc.openprojects.net.  Over time, many people contributed code, ideas, bugfixes, and a lot of alpha/beta/gamma testing.

     See the CREDITS file for a list of contributors.

  * 2003

     ERC 3.0 was released.

  * 2004

     ERC 4.0 was released.

  * 2005

     ERC 5.0 was released.  Michael Olson became the release manager and eventually the maintainer.

     After some discussion between him and the Emacs developers, it was decided to include ERC in Emacs.

  * 2006

     ERC 5.1 was released.  It was subsequently included in Emacs 22.

     ERC became an official GNU project, and development moved to https://sv.gnu.org/projects/erc.  We switched to using GNU Arch as our revision control system.  Our mailing list address changed as well.

  * 2007

     We switched to using git for our version control system.

  * 2009+

     Since about 2009, ERC is no longer developed as a separate project, but is maintained as part of Emacs.

Official IRC channels
---------------------

The official channels for GNU Emacs and ERC lived on the Freenode IRC network until June 2021, when they---along with the official IRC channels of the GNU Project, the Free Software Foundation, and many other free software communities---relocated to the Libera.Chat network in the aftermath of changes in governance and policies of Freenode in May and June 2021.  GNU and FSF's announcements about this are at https://lists.gnu.org/archive/html/info-gnu/2021-06/msg00005.html, https://lists.gnu.org/archive/html/info-gnu/2021-06/msg00007.html, and https://lists.gnu.org/archive/html/info-gnu-emacs/2021-06/msg00000.html.

GNU Free Documentation License
******************************

     [file doclicense.texi not included]