Some ircds send numeric 005 as part of the welcome message on connect. It contains
a list of tags that identify options the server supports, and is intended to help
scripters and client coders. I've seen more ircds sending this recently, and with
some client support appearing, I figured it was time to post a list.

This isn't a complete list, and doesn't go into details yet. I'll add more to it
when I have time. It does contain all tags that I'm presently aware of, except for
three: NOQUIT (has nothing to do with clients); SAFELIST (doesn't mean much anymore);
and HCN (no documentation). If you want me to dig up details, feel free to ask, but
keep in mind I'm not familiar with all of these myself, so I may not know :)

 
CHANMODES=a,b,c,d 

    Categorizes channel mode characters: 

        a - modes that take a parameter, and add/remove the parameter 
            to/from a list (such as 'b') 

        b - modes that take a parameter when set and unset (such as 'k') 

        c - modes that take a parameter only when set (such as 'l') 

        d - modes that do not take parameters (such as 'imnpst') 

    Example: CHANMODES=beI,k,l,cimnpRst 

    [ introduced by mIRC 5.9, not currently supported on any networks ] 

--- 
CHANTYPES=x 

    Indicates the prefixes of the supported channel types. 

    Prefix  Channel type 
       #    global, supports modes 
       +    global, modeless 
       &    local, supports modes 

    Example:  CHANTYPES=#& 

--- 
CPRIVMSG 

    Indicates support for the CPRIVMSG command. 

    Example: CPRIVMSG 

--- 
CNOTICE 

    Indicates support for the CNOTICE command. 

    Example: CNOTICE 

--- 
IRCX 

    Indicates support for the IRCX extensions. 

    Example: IRCX 

--- 
KICKLEN=n 

    Indicates the maximum number of characters a KICK reason may use. 

    Example: KICKLEN=160 

--- 
KNOCK 

    Indicates support for the KNOCK command. 

    Example: KNOCK 

--- 
MAP 

    Indicates support for the MAP command. 

    Example: MAP 

--- 
MAXBANS=n 

    Indicates the maximum number of bans that may be active in a channel at 
    any given time. 

    Example: MAXBANS=60 

--- 
MAXCHANNELS=n 

    Indicates the maximum number of channels a client may be a member of at 
    any given time. 

    Example: MAXCHANNELS=10 

--- 
MAXTARGETS=n 

    Indicates the maximum number of comma-separated targets a single message 
    may have. 

    Example: MAXTARGETS=4 

--- 
MODES=n 

    Indicates the maximum number of mode characters that may be specified in 
    a single command. 

    Example: MODES=6 

--- 
NICKLEN=n 

    Indicates the maximum number of characters a nickname may use. 

    Example: NICKLEN=30 

--- 
PREFIX=x 
PREFIX=(x)x 

    Indicates the available character prefixes for channel modes, and 
    optionally the mode characters that correspond with them. 

    Prefix  Mode  Description 
       @      o   channel operator 
       %      h   channel half-operator 
       +      v   channel voice 

    Example: PREFIX=@%+ 
    Example: PREFIX=(ohv)@%+ 

    Suggested assumption: modes are ordered right to left as highest rank to 
    lowest. 

--- 
SILENCE=n 

    Indicates the maximum number of masks that may be active in a SILENCE list 
    at any given time. 

    Example: SILENCE=5 

--- 
TOPICLEN=n 

    Indicates the maximum number of characters a channel topic may use. 

    Example: TOPICLEN=160 

--- 
USERIP 

    Indicates support for the USERIP command. 

    Example: USERIP 

--- 
VCHANS 

    Indicates support for virtual channels. 

    Example: VCHANS 

--- 
WALLCHOPS 

    Indicates support of the @ target, for sending the message 
    to all channel operators. 

    Example: WALLCHOPS 

--- 
WATCH=n 

    Indicates the maximum number of nicknames that may be in a watch list at 
    any given time. 

    Example: WATCH=128 

--- 
WHOX 

    Indicates support for WHO filtering extensions. 

    Example: WHOX