Channel modes are set with /mode <#channel> ±<modes> [parameters]
User modes are set with /mode <yournick> ±<modes>

Channel Modes

Mode Parameter Meaning Description
b hostmask Ban Prevents users matching hostmask from joining or talking in the channel
B action:minlen:percent Block caps Punishes messages containing more capital letters than the set threshold
c No color Messages containing formatting codes will not be sent to the channel.
C No CTCP Blocks channelwide CTCP requests
d seconds Delayed message User must be joined for seconds seconds to chat
D Delayed join Delays all JOIN messages from users until they become active or have a mode set
e hostmask Ban exceptions Matching users are not affected by bans
F num:sec Nick flood protection Allows only num nick changes within sec seconds
g badword Message filter Prevents messages containing badword
h nickname %Half-op Makes nickname an half-op. A half-op can't unmode or kick other operators or half-ops.
i Invite Joining the channel requires an invite from an operator (@)
I hostmask Invite exception Matching users does not require an invite to join an invite-only (+i) channel
j num:sec Join flood protection Closes the channel for a moment if number of joins exceeds num within sec seconds
J seconds Rejoin prevention Someone kicked from channel can't rejoin for seconds seconds
k password Key Joining the channel requires knowing the password (or "key")
l number Limit Only number users can be in the channel.
m Moderated Only operators (@) and voiced members (+) may speak.
M Moderated Only authenticated users may speak, in addition to operators (@) and voiced members (+).
n No external messages Users have to be in the channel to talk in it.
o nickname @Operator Makes nickname an operator in the channel.
p Private Channel will be hidden in /WHOIS replies.
R Registration required Only authenticated users can join the channel.
s Secret Channel will be hidden in /LIST and /WHOIS replies.
S Strip formatting Strips any formatting codes from messages
t Topic lock Only operators can change the topic.
T hostmask Block notice Blocks matching users from sending notices to the channel
u Auditorium mode Makes everybody else in the channel invisible
v nickname +Voice nickname can speak when channel is moderated
w mode:mask Basic automode Gives mode to users matching mask on join. mask can be hostmask or use extban format
X rule:mode Exempt chanops Allows users with a specified channel mode (o or v) to be excempt from some channel restrictions
z SSL only All members of the channel must be connected via TLS (SSL)

User Modes

Mode Meaning Description
B Bot /WHOIS on someone with this mode set will say user is a robot
c Common chan Only accept messages from users in a same channel
d Deaf Mutes all channel messages
i Invisible Prevents user from showing in /WHO and /NAMES replies
R Registered only Only accept messages from authenticated users
S Strip formatting Removes color codes from incoming messages and notices
T No CTCP Blocks CTCP requests
w Wallops See certain messages sent by the IRC operators
x Cloaked IP Cloaks IP or host.
z Secure Only accept private messages from users connected via SSL