This page attempts to document the unique behaviors that mIRC will exhibit in response to server and network specific supported features. Features are often expressed via ISUPPORT 005 numeric (type /raw VERSION), or via CAP LS, REQ, LIST handshake (type /raw CAP LS). There are other signals that mIRC picks up during an IRC session that modifies its behaviors in how it handles network specific features or idiosyncrasies.

The goal is to document all the various deviations of expected behaviors in order to anticipate and understand them better.

005 ISUPPORT

CPRIVMSG / CNOTICE

If CPRIVMSG or CNOTICE appears in the 005 ISUPPORT list, then any time you are an op or voice in a channel that you share with another user that you wish to send a query (/msg, /query, ctcp) or notice (/notice, /ctcpreply) to, the IRC command CPRIVMSG will be used instead of PRIVMSG, and CNOTICE will be used instead of NOTICE. These commands enable you, as an opped or voiced user, to bypass certain server restrictions for the number of users you can message in a short period of time, or how much text you can send to them in a short period of time, or whether you need to gain the user's permission first before you are allowed to send them a message... depending on server implementation.

mIRC v7.53 29-Nov-2018
21.Added support for CPRIVMSG and CNOTICE. If listed in numeric 005,
   PRIVMSG and NOTICE will be automatically upgraded for most
   outgoing messages if you are an op/voice on a channel and message
   a user on the same channel.

NAMESX

If NAMESX appears in the 005 ISUPPORT list, then mIRC will immediately issue the command 'PROTOCTL NAMESX' to request NAMESX support. This will enable multi-prefix support by telling the server to display multiple prefix in NAMES responses, ie, when joining a channel. Though mIRC doesn't display the multiple prefixes on the user interface, they will be tracked internally and be known to scripts using 'isvoice' and '$nick(#,%i,v)' etc when a user is both an op and a voice.

mIRC v6.17 17-Feb-2006
18.Added support for numeric 005 NAMESX token, indicating that
   mIRC supports multiple mode prefixes for a nickname in a NAMES
   list, eg. @+nickname.