diff --git a/irc/channel.go b/irc/channel.go
index 7153277a..d3f34d0b 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -439,8 +439,12 @@ func (channel *Channel) regenerateMembersCache() {
 
 // Names sends the list of users joined to the channel to the given client.
 func (channel *Channel) Names(client *Client, rb *ResponseBuffer) {
-	isJoined := channel.hasClient(client)
+	channel.stateMutex.RLock()
+	clientModes, isJoined := channel.members[client]
+	channel.stateMutex.RUnlock()
 	isOper := client.HasMode(modes.Operator)
+	respectAuditorium := channel.flags.HasMode(modes.Auditorium) && !isOper &&
+		(!isJoined || clientModes.HighestChannelUserMode() == modes.Mode(0))
 	isMultiPrefix := rb.session.capabilities.Has(caps.MultiPrefix)
 	isUserhostInNames := rb.session.capabilities.Has(caps.UserhostInNames)
 
@@ -464,6 +468,9 @@ func (channel *Channel) Names(client *Client, rb *ResponseBuffer) {
 			if !isJoined && target.HasMode(modes.Invisible) && !isOper {
 				continue
 			}
+			if respectAuditorium && modeSet.HighestChannelUserMode() == modes.Mode(0) {
+				continue
+			}
 			prefix := modeSet.Prefixes(isMultiPrefix)
 			if buffer.Len()+len(nick)+len(prefix)+1 > maxNamLen {
 				namesLines = append(namesLines, buffer.String())
@@ -748,8 +755,9 @@ func (channel *Channel) Join(client *Client, key string, isSajoin bool, rb *Resp
 	}()
 
 	var message utils.SplitMessage
+	respectAuditorium := givenMode == modes.Mode(0) && channel.flags.HasMode(modes.Auditorium)
 	// no history item for fake persistent joins
-	if rb != nil {
+	if rb != nil && !respectAuditorium {
 		message = utils.MakeMessage("")
 		histItem := history.Item{
 			Type:        history.Join,
@@ -772,6 +780,14 @@ func (channel *Channel) Join(client *Client, key string, isSajoin bool, rb *Resp
 
 	isAway, awayMessage := client.Away()
 	for _, member := range channel.Members() {
+		if respectAuditorium {
+			channel.stateMutex.RLock()
+			memberModes, ok := channel.members[member]
+			channel.stateMutex.RUnlock()
+			if !ok || memberModes.HighestChannelUserMode() == modes.Mode(0) {
+				continue
+			}
+		}
 		for _, session := range member.Sessions() {
 			if session == rb.session {
 				continue
@@ -889,8 +905,12 @@ func (channel *Channel) playJoinForSession(session *Session) {
 
 // Part parts the given client from this channel, with the given message.
 func (channel *Channel) Part(client *Client, message string, rb *ResponseBuffer) {
-	chname := channel.Name()
-	if !channel.hasClient(client) {
+	channel.stateMutex.RLock()
+	chname := channel.name
+	clientModes, ok := channel.members[client]
+	channel.stateMutex.RUnlock()
+
+	if !ok {
 		rb.Add(nil, client.server.name, ERR_NOTONCHANNEL, client.Nick(), chname, client.t("You're not on that channel"))
 		return
 	}
@@ -905,7 +925,17 @@ func (channel *Channel) Part(client *Client, message string, rb *ResponseBuffer)
 	if message != "" {
 		params = append(params, message)
 	}
+	respectAuditorium := channel.flags.HasMode(modes.Auditorium) &&
+		clientModes.HighestChannelUserMode() == modes.Mode(0)
 	for _, member := range channel.Members() {
+		if respectAuditorium {
+			channel.stateMutex.RLock()
+			memberModes, ok := channel.members[member]
+			channel.stateMutex.RUnlock()
+			if !ok || memberModes.HighestChannelUserMode() == modes.Mode(0) {
+				continue
+			}
+		}
 		member.sendFromClientInternal(false, splitMessage.Time, splitMessage.Msgid, details.nickMask, details.accountName, nil, "PART", params...)
 	}
 	rb.AddFromClient(splitMessage.Time, splitMessage.Msgid, details.nickMask, details.accountName, nil, "PART", params...)
@@ -915,12 +945,14 @@ func (channel *Channel) Part(client *Client, message string, rb *ResponseBuffer)
 		}
 	}
 
-	channel.AddHistoryItem(history.Item{
-		Type:        history.Part,
-		Nick:        details.nickMask,
-		AccountName: details.accountName,
-		Message:     splitMessage,
-	}, details.account)
+	if !respectAuditorium {
+		channel.AddHistoryItem(history.Item{
+			Type:        history.Part,
+			Nick:        details.nickMask,
+			AccountName: details.accountName,
+			Message:     splitMessage,
+		}, details.account)
+	}
 
 	client.server.logger.Debug("part", fmt.Sprintf("%s left channel %s", details.nick, chname))
 }
@@ -951,20 +983,24 @@ func (channel *Channel) resumeAndAnnounce(session *Session) {
 	// send join for old clients
 	chname := channel.Name()
 	details := session.client.Details()
-	for _, member := range channel.Members() {
-		for _, session := range member.Sessions() {
-			if session.capabilities.Has(caps.Resume) {
-				continue
-			}
+	// TODO: for now, skip this entirely for auditoriums,
+	// but really we should send it to voiced clients
+	if !channel.flags.HasMode(modes.Auditorium) {
+		for _, member := range channel.Members() {
+			for _, session := range member.Sessions() {
+				if session.capabilities.Has(caps.Resume) {
+					continue
+				}
 
-			if session.capabilities.Has(caps.ExtendedJoin) {
-				session.Send(nil, details.nickMask, "JOIN", chname, details.accountName, details.realname)
-			} else {
-				session.Send(nil, details.nickMask, "JOIN", chname)
-			}
+				if session.capabilities.Has(caps.ExtendedJoin) {
+					session.Send(nil, details.nickMask, "JOIN", chname, details.accountName, details.realname)
+				} else {
+					session.Send(nil, details.nickMask, "JOIN", chname)
+				}
 
-			if 0 < len(oldModes) {
-				session.Send(nil, channel.server.name, "MODE", chname, oldModes, details.nick)
+				if 0 < len(oldModes) {
+					session.Send(nil, channel.server.name, "MODE", chname, oldModes, details.nick)
+				}
 			}
 		}
 	}
@@ -1451,6 +1487,30 @@ func (channel *Channel) Invite(invitee *Client, inviter *Client, rb *ResponseBuf
 	}
 }
 
+// returns who the client can "see" in the channel, respecting the auditorium mode
+func (channel *Channel) auditoriumFriends(client *Client) (friends []*Client) {
+	channel.stateMutex.RLock()
+	defer channel.stateMutex.RUnlock()
+
+	clientModes := channel.members[client]
+	if clientModes == nil {
+		return // non-members have no friends
+	}
+	if !channel.flags.HasMode(modes.Auditorium) {
+		return channel.membersCache // default behavior for members
+	}
+	if clientModes.HighestChannelUserMode() != modes.Mode(0) {
+		return channel.membersCache // +v and up can see everyone in the auditorium
+	}
+	// without +v, your friends are those with +v and up
+	for member, memberModes := range channel.members {
+		if memberModes.HighestChannelUserMode() != modes.Mode(0) {
+			friends = append(friends, member)
+		}
+	}
+	return
+}
+
 // data for RPL_LIST
 func (channel *Channel) listData() (memberCount int, name, topic string) {
 	channel.stateMutex.RLock()
diff --git a/irc/client.go b/irc/client.go
index da4829e5..40406fda 100644
--- a/irc/client.go
+++ b/irc/client.go
@@ -934,7 +934,7 @@ func (session *Session) playResume() {
 	// work out how much time, if any, is not covered by history buffers
 	// assume that a persistent buffer covers the whole resume period
 	for _, channel := range client.Channels() {
-		for _, member := range channel.Members() {
+		for _, member := range channel.auditoriumFriends(client) {
 			friends.Add(member)
 		}
 		status, _ := channel.historyStatus(config)
@@ -1161,7 +1161,7 @@ func (client *Client) Friends(capabs ...caps.Capability) (result map[*Session]em
 	addFriendsToSet(result, client, capabs...)
 
 	for _, channel := range client.Channels() {
-		for _, member := range channel.Members() {
+		for _, member := range channel.auditoriumFriends(client) {
 			addFriendsToSet(result, member, capabs...)
 		}
 	}
@@ -1512,10 +1512,10 @@ func (client *Client) destroy(session *Session) {
 	friends := make(ClientSet)
 	channels = client.Channels()
 	for _, channel := range channels {
-		channel.Quit(client)
-		for _, member := range channel.Members() {
+		for _, member := range channel.auditoriumFriends(client) {
 			friends.Add(member)
 		}
+		channel.Quit(client)
 	}
 	friends.Remove(client)
 
diff --git a/irc/handlers.go b/irc/handlers.go
index 89604db2..431a6c7d 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -3051,7 +3051,13 @@ func whoHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Respo
 		if channel != nil {
 			isJoined := channel.hasClient(client)
 			if !channel.flags.HasMode(modes.Secret) || isJoined || isOper {
-				for _, member := range channel.Members() {
+				var members []*Client
+				if isOper {
+					members = channel.Members()
+				} else {
+					members = channel.auditoriumFriends(client)
+				}
+				for _, member := range members {
 					if !member.HasMode(modes.Invisible) || isJoined || isOper {
 						client.rplWhoReply(channel, member, rb, isWhox, fields, whoType)
 					}
@@ -3072,6 +3078,9 @@ func whoHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Respo
 			}
 
 			for _, channel := range otherClient.Channels() {
+				if channel.flags.HasMode(modes.Auditorium) {
+					return false // TODO this should respect +v etc.
+				}
 				if _, present := userChannels[channel]; present {
 					return true
 				}
diff --git a/irc/help.go b/irc/help.go
index 62b7d81f..8e9801a3 100644
--- a/irc/help.go
+++ b/irc/help.go
@@ -54,6 +54,8 @@ Oragono supports the following channel modes:
   +t  |  Only channel opers can modify the topic.
   +E  |  Roleplaying commands are enabled in the channel.
   +C  |  Clients are blocked from sending CTCP messages in the channel.
+  +u  |  Auditorium mode: JOIN, PART, QUIT, NAMES, and WHO are hidden
+         hidden from unvoiced clients.
 
 = Prefixes =
 
@@ -74,7 +76,7 @@ Oragono supports the following user modes:
   +Z  |  User is connected via TLS.
   +B  |  User is a bot.
   +E  |  User can receive roleplaying commands.
-  +T  |  User is blocked from sending CTCP messages.`
+  +T  |  CTCP messages to the user are blocked.`
 	snomaskHelpText = `== Server Notice Masks ==
 
 Oragono supports the following server notice masks for operators:
diff --git a/irc/modes/modes.go b/irc/modes/modes.go
index 0dfbe5f6..237ef0ca 100644
--- a/irc/modes/modes.go
+++ b/irc/modes/modes.go
@@ -23,7 +23,7 @@ var (
 	SupportedChannelModes = Modes{
 		BanMask, ChanRoleplaying, ExceptMask, InviteMask, InviteOnly, Key,
 		Moderated, NoOutside, OpOnlyTopic, RegisteredOnly, RegisteredOnlySpeak,
-		Secret, UserLimit, NoCTCP,
+		Secret, UserLimit, NoCTCP, Auditorium,
 	}
 )
 
@@ -113,6 +113,7 @@ const (
 
 // Channel Modes
 const (
+	Auditorium      Mode = 'u' // flag
 	BanMask         Mode = 'b' // arg
 	ChanRoleplaying Mode = 'E' // flag
 	ExceptMask      Mode = 'e' // arg
diff --git a/irctest b/irctest
index 0287b837..616785ea 160000
--- a/irctest
+++ b/irctest
@@ -1 +1 @@
-Subproject commit 0287b837971c27ee55bc4dca95d31afc68d2aeea
+Subproject commit 616785eae403536954f1b1181f74ef51343e33f7