diff --git a/irc/capability.go b/irc/capability.go
index fa4ba9b8..afb4760e 100644
--- a/irc/capability.go
+++ b/irc/capability.go
@@ -13,28 +13,12 @@ import (
 
 var (
 	// SupportedCapabilities are the caps we advertise.
-	SupportedCapabilities = CapabilitySet{
-		caps.AccountTag:    true,
-		caps.AccountNotify: true,
-		caps.AwayNotify:    true,
-		caps.CapNotify:     true,
-		caps.ChgHost:       true,
-		caps.EchoMessage:   true,
-		caps.ExtendedJoin:  true,
-		caps.InviteNotify:  true,
-		// MaxLine is set during server startup
-		caps.MessageTags: true,
-		caps.MultiPrefix: true,
-		caps.Rename:      true,
-		// SASL is set during server startup
-		caps.ServerTime: true,
-		// STS is set during server startup
-		caps.UserhostInNames: true,
-	}
+	// MaxLine, SASL and STS are set during server startup.
+	SupportedCapabilities = caps.NewSet(caps.AccountTag, caps.AccountNotify, caps.AwayNotify, caps.CapNotify, caps.ChgHost, caps.EchoMessage, caps.ExtendedJoin, caps.InviteNotify, caps.MessageTags, caps.MultiPrefix, caps.Rename, caps.ServerTime, caps.UserhostInNames)
+
 	// CapValues are the actual values we advertise to v3.2 clients.
-	CapValues = map[caps.Capability]string{
-		caps.SASL: "PLAIN,EXTERNAL",
-	}
+	// actual values are set during server startup.
+	CapValues = caps.NewValues()
 )
 
 // CapState shows whether we're negotiating caps, finished, etc for connection registration.
@@ -49,40 +33,10 @@ const (
 	CapNegotiated CapState = iota
 )
 
-// CapVersion is used to select which max version of CAP the client supports.
-type CapVersion uint
-
-const (
-	// Cap301 refers to the base CAP spec.
-	Cap301 CapVersion = 301
-	// Cap302 refers to the IRCv3.2 CAP spec.
-	Cap302 CapVersion = 302
-)
-
-// CapabilitySet is used to track supported, enabled, and existing caps.
-type CapabilitySet map[caps.Capability]bool
-
-func (set CapabilitySet) String(version CapVersion) string {
-	strs := make([]string, len(set))
-	index := 0
-	for capability := range set {
-		capString := string(capability)
-		if version == Cap302 {
-			val, exists := CapValues[capability]
-			if exists {
-				capString += "=" + val
-			}
-		}
-		strs[index] = capString
-		index++
-	}
-	return strings.Join(strs, " ")
-}
-
 // CAP <subcmd> [<caps>]
 func capHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 	subCommand := strings.ToUpper(msg.Params[0])
-	capabilities := make(CapabilitySet)
+	capabilities := caps.NewSet()
 	var capString string
 
 	if len(msg.Params) > 1 {
@@ -90,7 +44,7 @@ func capHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 		strs := strings.Split(capString, " ")
 		for _, str := range strs {
 			if len(str) > 0 {
-				capabilities[caps.Capability(str)] = true
+				capabilities.Enable(caps.Capability(str))
 			}
 		}
 	}
@@ -107,22 +61,20 @@ func capHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 		// the server.name source... otherwise it doesn't respond to the CAP message with
 		// anything and just hangs on connection.
 		//TODO(dan): limit number of caps and send it multiline in 3.2 style as appropriate.
-		client.Send(nil, server.name, "CAP", client.nick, subCommand, SupportedCapabilities.String(client.capVersion))
+		client.Send(nil, server.name, "CAP", client.nick, subCommand, SupportedCapabilities.String(client.capVersion, CapValues))
 
 	case "LIST":
-		client.Send(nil, server.name, "CAP", client.nick, subCommand, client.capabilities.String(Cap301)) // values not sent on LIST so force 3.1
+		client.Send(nil, server.name, "CAP", client.nick, subCommand, client.capabilities.String(caps.Cap301, CapValues)) // values not sent on LIST so force 3.1
 
 	case "REQ":
 		// make sure all capabilities actually exist
-		for capability := range capabilities {
-			if !SupportedCapabilities[capability] {
+		for _, capability := range capabilities.List() {
+			if !SupportedCapabilities.Has(capability) {
 				client.Send(nil, server.name, "CAP", client.nick, "NAK", capString)
 				return false
 			}
 		}
-		for capability := range capabilities {
-			client.capabilities[capability] = true
-		}
+		client.capabilities.Enable(capabilities.List()...)
 		client.Send(nil, server.name, "CAP", client.nick, "ACK", capString)
 
 	case "END":
diff --git a/irc/caps/constants.go b/irc/caps/constants.go
index 523b07af..c43b84be 100644
--- a/irc/caps/constants.go
+++ b/irc/caps/constants.go
@@ -45,6 +45,7 @@ const (
 	UserhostInNames Capability = "userhost-in-names"
 )
 
-func (capability Capability) String() string {
+// Name returns the name of the given capability.
+func (capability Capability) Name() string {
 	return string(capability)
 }
diff --git a/irc/caps/set.go b/irc/caps/set.go
new file mode 100644
index 00000000..c5ad4207
--- /dev/null
+++ b/irc/caps/set.go
@@ -0,0 +1,115 @@
+// Package caps holds capabilities.
+package caps
+
+import (
+	"sort"
+	"strings"
+	"sync"
+)
+
+// Set holds a set of enabled capabilities.
+type Set struct {
+	sync.RWMutex
+	// capabilities holds the capabilities this manager has.
+	capabilities map[Capability]bool
+}
+
+// NewSet returns a new Set, with the given capabilities enabled.
+func NewSet(capabs ...Capability) *Set {
+	newSet := Set{
+		capabilities: make(map[Capability]bool),
+	}
+	newSet.Enable(capabs...)
+
+	return &newSet
+}
+
+// Enable enables the given capabilities.
+func (s *Set) Enable(capabs ...Capability) {
+	s.Lock()
+	defer s.Unlock()
+
+	for _, capab := range capabs {
+		s.capabilities[capab] = true
+	}
+}
+
+// Disable disables the given capabilities.
+func (s *Set) Disable(capabs ...Capability) {
+	s.Lock()
+	defer s.Unlock()
+
+	for _, capab := range capabs {
+		delete(s.capabilities, capab)
+	}
+}
+
+// Add adds the given capabilities to this set.
+// this is just a wrapper to allow more clear use.
+func (s *Set) Add(capabs ...Capability) {
+	s.Enable(capabs...)
+}
+
+// Remove removes the given capabilities from this set.
+// this is just a wrapper to allow more clear use.
+func (s *Set) Remove(capabs ...Capability) {
+	s.Disable(capabs...)
+}
+
+// Has returns true if this set has the given capabilities.
+func (s *Set) Has(caps ...Capability) bool {
+	s.RLock()
+	defer s.RUnlock()
+
+	for _, cap := range caps {
+		if !s.capabilities[cap] {
+			return false
+		}
+	}
+	return true
+}
+
+// List return a list of our enabled capabilities.
+func (s *Set) List() []Capability {
+	s.RLock()
+	defer s.RUnlock()
+
+	var allCaps []Capability
+	for capab := range s.capabilities {
+		allCaps = append(allCaps, capab)
+	}
+
+	return allCaps
+}
+
+// Count returns how many enabled caps this set has.
+func (s *Set) Count() int {
+	s.RLock()
+	defer s.RUnlock()
+
+	return len(s.capabilities)
+}
+
+// String returns all of our enabled capabilities as a string.
+func (s *Set) String(version Version, values *Values) string {
+	s.RLock()
+	defer s.RUnlock()
+
+	var strs sort.StringSlice
+
+	for capability := range s.capabilities {
+		capString := capability.Name()
+		if version == Cap302 {
+			val, exists := values.Get(capability)
+			if exists {
+				capString += "=" + val
+			}
+		}
+		strs = append(strs, capString)
+	}
+
+	// sort the cap string before we send it out
+	sort.Sort(strs)
+
+	return strings.Join(strs, " ")
+}
diff --git a/irc/caps/values.go b/irc/caps/values.go
new file mode 100644
index 00000000..e8fb9979
--- /dev/null
+++ b/irc/caps/values.go
@@ -0,0 +1,42 @@
+package caps
+
+import "sync"
+
+// Values holds capability values.
+type Values struct {
+	sync.RWMutex
+	// values holds our actual capability values.
+	values map[Capability]string
+}
+
+// NewValues returns a new Values.
+func NewValues() *Values {
+	return &Values{
+		values: make(map[Capability]string),
+	}
+}
+
+// Set sets the value for the given capability.
+func (v *Values) Set(capab Capability, value string) {
+	v.Lock()
+	defer v.Unlock()
+
+	v.values[capab] = value
+}
+
+// Unset removes the value for the given capability, if it exists.
+func (v *Values) Unset(capab Capability) {
+	v.Lock()
+	defer v.Unlock()
+
+	delete(v.values, capab)
+}
+
+// Get returns the value of the given capability, and whether one exists.
+func (v *Values) Get(capab Capability) (string, bool) {
+	v.RLock()
+	defer v.RUnlock()
+
+	value, exists := v.values[capab]
+	return value, exists
+}
diff --git a/irc/caps/version.go b/irc/caps/version.go
new file mode 100644
index 00000000..b718f2fa
--- /dev/null
+++ b/irc/caps/version.go
@@ -0,0 +1,11 @@
+package caps
+
+// Version is used to select which max version of CAP the client supports.
+type Version uint
+
+const (
+	// Cap301 refers to the base CAP spec.
+	Cap301 Version = 301
+	// Cap302 refers to the IRCv3.2 CAP spec.
+	Cap302 Version = 302
+)
diff --git a/irc/channel.go b/irc/channel.go
index eba86d7d..94f6c280 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -165,8 +165,8 @@ func (modes ModeSet) Prefixes(isMultiPrefix bool) string {
 }
 
 func (channel *Channel) nicksNoMutex(target *Client) []string {
-	isMultiPrefix := (target != nil) && target.capabilities[caps.MultiPrefix]
-	isUserhostInNames := (target != nil) && target.capabilities[caps.UserhostInNames]
+	isMultiPrefix := (target != nil) && target.capabilities.Has(caps.MultiPrefix)
+	isUserhostInNames := (target != nil) && target.capabilities.Has(caps.UserhostInNames)
 	nicks := make([]string, len(channel.members))
 	i := 0
 	for client, modes := range channel.members {
@@ -262,7 +262,7 @@ func (channel *Channel) Join(client *Client, key string) {
 	client.server.logger.Debug("join", fmt.Sprintf("%s joined channel %s", client.nick, channel.name))
 
 	for member := range channel.members {
-		if member.capabilities[caps.ExtendedJoin] {
+		if member.capabilities.Has(caps.ExtendedJoin) {
 			member.Send(nil, client.nickMaskString, "JOIN", channel.name, client.account.Name, client.realname)
 		} else {
 			member.Send(nil, client.nickMaskString, "JOIN", channel.name)
@@ -314,7 +314,7 @@ func (channel *Channel) Join(client *Client, key string) {
 		return nil
 	})
 
-	if client.capabilities[caps.ExtendedJoin] {
+	if client.capabilities.Has(caps.ExtendedJoin) {
 		client.Send(nil, client.nickMaskString, "JOIN", channel.name, client.account.Name, client.realname)
 	} else {
 		client.Send(nil, client.nickMaskString, "JOIN", channel.name)
@@ -465,13 +465,13 @@ func (channel *Channel) sendMessage(msgid, cmd string, requiredCaps []caps.Capab
 			// STATUSMSG
 			continue
 		}
-		if member == client && !client.capabilities[caps.EchoMessage] {
+		if member == client && !client.capabilities.Has(caps.EchoMessage) {
 			continue
 		}
 
 		canReceive := true
 		for _, capName := range requiredCaps {
-			if !member.capabilities[capName] {
+			if !member.capabilities.Has(capName) {
 				canReceive = false
 			}
 		}
@@ -480,7 +480,7 @@ func (channel *Channel) sendMessage(msgid, cmd string, requiredCaps []caps.Capab
 		}
 
 		var messageTagsToUse *map[string]ircmsg.TagValue
-		if member.capabilities[caps.MessageTags] {
+		if member.capabilities.Has(caps.MessageTags) {
 			messageTagsToUse = clientOnlyTags
 		}
 
@@ -521,11 +521,11 @@ func (channel *Channel) sendSplitMessage(msgid, cmd string, minPrefix *Mode, cli
 			// STATUSMSG
 			continue
 		}
-		if member == client && !client.capabilities[caps.EchoMessage] {
+		if member == client && !client.capabilities.Has(caps.EchoMessage) {
 			continue
 		}
 		var tagsToUse *map[string]ircmsg.TagValue
-		if member.capabilities[caps.MessageTags] {
+		if member.capabilities.Has(caps.MessageTags) {
 			tagsToUse = clientOnlyTags
 		}
 
@@ -729,7 +729,7 @@ func (channel *Channel) Invite(invitee *Client, inviter *Client) {
 
 	// send invite-notify
 	for member := range channel.members {
-		if member.capabilities[caps.InviteNotify] && member != inviter && member != invitee && channel.ClientIsAtLeast(member, Halfop) {
+		if member.capabilities.Has(caps.InviteNotify) && member != inviter && member != invitee && channel.ClientIsAtLeast(member, Halfop) {
 			member.Send(nil, inviter.nickMaskString, "INVITE", invitee.nick, channel.name)
 		}
 	}
diff --git a/irc/client.go b/irc/client.go
index f19c0467..04172f97 100644
--- a/irc/client.go
+++ b/irc/client.go
@@ -45,9 +45,9 @@ type Client struct {
 	atime              time.Time
 	authorized         bool
 	awayMessage        string
-	capabilities       CapabilitySet
+	capabilities       *caps.Set
 	capState           CapState
-	capVersion         CapVersion
+	capVersion         caps.Version
 	certfp             string
 	channels           ChannelSet
 	class              *OperClass
@@ -95,9 +95,9 @@ func NewClient(server *Server, conn net.Conn, isTLS bool) *Client {
 	client := &Client{
 		atime:          now,
 		authorized:     server.password == nil,
-		capabilities:   make(CapabilitySet),
+		capabilities:   caps.NewSet(),
 		capState:       CapNone,
-		capVersion:     Cap301,
+		capVersion:     caps.Cap301,
 		channels:       make(ChannelSet),
 		ctime:          now,
 		flags:          make(map[Mode]bool),
@@ -178,10 +178,10 @@ func (client *Client) IPString() string {
 func (client *Client) maxlens() (int, int) {
 	maxlenTags := 512
 	maxlenRest := 512
-	if client.capabilities[caps.MessageTags] {
+	if client.capabilities.Has(caps.MessageTags) {
 		maxlenTags = 4096
 	}
-	if client.capabilities[caps.MaxLine] {
+	if client.capabilities.Has(caps.MaxLine) {
 		if client.server.limits.LineLen.Tags > maxlenTags {
 			maxlenTags = client.server.limits.LineLen.Tags
 		}
@@ -357,13 +357,13 @@ func (client *Client) ModeString() (str string) {
 }
 
 // Friends refers to clients that share a channel with this client.
-func (client *Client) Friends(Capabilities ...caps.Capability) ClientSet {
+func (client *Client) Friends(capabs ...caps.Capability) ClientSet {
 	friends := make(ClientSet)
 
 	// make sure that I have the right caps
 	hasCaps := true
-	for _, Cap := range Capabilities {
-		if !client.capabilities[Cap] {
+	for _, capab := range capabs {
+		if !client.capabilities.Has(capab) {
 			hasCaps = false
 			break
 		}
@@ -377,8 +377,8 @@ func (client *Client) Friends(Capabilities ...caps.Capability) ClientSet {
 		for member := range channel.members {
 			// make sure they have all the required caps
 			hasCaps = true
-			for _, Cap := range Capabilities {
-				if !member.capabilities[Cap] {
+			for _, capab := range capabs {
+				if !member.capabilities.Has(capab) {
 					hasCaps = false
 					break
 				}
@@ -580,7 +580,7 @@ func (client *Client) destroy() {
 // SendSplitMsgFromClient sends an IRC PRIVMSG/NOTICE coming from a specific client.
 // Adds account-tag to the line as well.
 func (client *Client) SendSplitMsgFromClient(msgid string, from *Client, tags *map[string]ircmsg.TagValue, command, target string, message SplitMessage) {
-	if client.capabilities[caps.MaxLine] {
+	if client.capabilities.Has(caps.MaxLine) {
 		client.SendFromClient(msgid, from, tags, command, target, message.ForMaxLine)
 	} else {
 		for _, str := range message.For512 {
@@ -593,7 +593,7 @@ func (client *Client) SendSplitMsgFromClient(msgid string, from *Client, tags *m
 // Adds account-tag to the line as well.
 func (client *Client) SendFromClient(msgid string, from *Client, tags *map[string]ircmsg.TagValue, command string, params ...string) error {
 	// attach account-tag
-	if client.capabilities[caps.AccountTag] && from.account != &NoAccount {
+	if client.capabilities.Has(caps.AccountTag) && from.account != &NoAccount {
 		if tags == nil {
 			tags = ircmsg.MakeTags("account", from.account.Name)
 		} else {
@@ -601,7 +601,7 @@ func (client *Client) SendFromClient(msgid string, from *Client, tags *map[strin
 		}
 	}
 	// attach message-id
-	if len(msgid) > 0 && client.capabilities[caps.MessageTags] {
+	if len(msgid) > 0 && client.capabilities.Has(caps.MessageTags) {
 		if tags == nil {
 			tags = ircmsg.MakeTags("draft/msgid", msgid)
 		} else {
@@ -628,7 +628,7 @@ var (
 // Send sends an IRC line to the client.
 func (client *Client) Send(tags *map[string]ircmsg.TagValue, prefix string, command string, params ...string) error {
 	// attach server-time
-	if client.capabilities[caps.ServerTime] {
+	if client.capabilities.Has(caps.ServerTime) {
 		t := time.Now().UTC().Format("2006-01-02T15:04:05.999Z")
 		if tags == nil {
 			tags = ircmsg.MakeTags("time", t)
@@ -678,7 +678,7 @@ func (client *Client) Send(tags *map[string]ircmsg.TagValue, prefix string, comm
 // Notice sends the client a notice from the server.
 func (client *Client) Notice(text string) {
 	limit := 400
-	if client.capabilities[caps.MaxLine] {
+	if client.capabilities.Has(caps.MaxLine) {
 		limit = client.server.limits.LineLen.Rest - 110
 	}
 	lines := wordWrap(text, limit)
diff --git a/irc/client_lookup_set.go b/irc/client_lookup_set.go
index 74cf8114..11cc0332 100644
--- a/irc/client_lookup_set.go
+++ b/irc/client_lookup_set.go
@@ -156,7 +156,7 @@ func (clients *ClientLookupSet) Replace(oldNick, newNick string, client *Client)
 }
 
 // AllWithCaps returns all clients with the given capabilities.
-func (clients *ClientLookupSet) AllWithCaps(caps ...caps.Capability) (set ClientSet) {
+func (clients *ClientLookupSet) AllWithCaps(capabs ...caps.Capability) (set ClientSet) {
 	set = make(ClientSet)
 
 	clients.ByNickMutex.RLock()
@@ -164,8 +164,8 @@ func (clients *ClientLookupSet) AllWithCaps(caps ...caps.Capability) (set Client
 	var client *Client
 	for _, client = range clients.ByNick {
 		// make sure they have all the required caps
-		for _, Cap := range caps {
-			if !client.capabilities[Cap] {
+		for _, capab := range capabs {
+			if !client.capabilities.Has(capab) {
 				continue
 			}
 		}
diff --git a/irc/roleplay.go b/irc/roleplay.go
index 9f1be9fc..d5d14d4d 100644
--- a/irc/roleplay.go
+++ b/irc/roleplay.go
@@ -90,7 +90,7 @@ func sendRoleplayMessage(server *Server, client *Client, source string, targetSt
 
 		channel.membersMutex.RLock()
 		for member := range channel.members {
-			if member == client && !client.capabilities[caps.EchoMessage] {
+			if member == client && !client.capabilities.Has(caps.EchoMessage) {
 				continue
 			}
 			member.Send(nil, source, "PRIVMSG", channel.name, message)
@@ -110,7 +110,7 @@ func sendRoleplayMessage(server *Server, client *Client, source string, targetSt
 		}
 
 		user.Send(nil, source, "PRIVMSG", user.nick, message)
-		if client.capabilities[caps.EchoMessage] {
+		if client.capabilities.Has(caps.EchoMessage) {
 			client.Send(nil, source, "PRIVMSG", user.nick, message)
 		}
 		if user.flags[Away] {
diff --git a/irc/server.go b/irc/server.go
index 788a4054..7d9feabf 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -642,11 +642,11 @@ func renameHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 
 	// send RENAME messages
 	for mcl := range channel.members {
-		if mcl.capabilities[caps.Rename] {
+		if mcl.capabilities.Has(caps.Rename) {
 			mcl.Send(nil, client.nickMaskString, "RENAME", oldName, newName, reason)
 		} else {
 			mcl.Send(nil, mcl.nickMaskString, "PART", oldName, fmt.Sprintf("Channel renamed: %s", reason))
-			if mcl.capabilities[caps.ExtendedJoin] {
+			if mcl.capabilities.Has(caps.ExtendedJoin) {
 				accountName := "*"
 				if mcl.account != nil {
 					accountName = mcl.account.Name
@@ -825,7 +825,7 @@ func privmsgHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool
 	message := msg.Params[1]
 
 	// split privmsg
-	splitMsg := server.splitMessage(message, !client.capabilities[caps.MaxLine])
+	splitMsg := server.splitMessage(message, !client.capabilities.Has(caps.MaxLine))
 
 	for i, targetString := range targets {
 		// max of four targets per privmsg
@@ -869,7 +869,7 @@ func privmsgHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool
 				}
 				continue
 			}
-			if !user.capabilities[caps.MessageTags] {
+			if !user.capabilities.Has(caps.MessageTags) {
 				clientOnlyTags = nil
 			}
 			msgid := server.generateMessageID()
@@ -878,7 +878,7 @@ func privmsgHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool
 			if !user.flags[RegisteredOnly] || client.registered {
 				user.SendSplitMsgFromClient(msgid, client, clientOnlyTags, "PRIVMSG", user.nick, splitMsg)
 			}
-			if client.capabilities[caps.EchoMessage] {
+			if client.capabilities.Has(caps.EchoMessage) {
 				client.SendSplitMsgFromClient(msgid, client, clientOnlyTags, "PRIVMSG", user.nick, splitMsg)
 			}
 			if user.flags[Away] {
@@ -939,11 +939,11 @@ func tagmsgHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 			msgid := server.generateMessageID()
 
 			// end user can't receive tagmsgs
-			if !user.capabilities[caps.MessageTags] {
+			if !user.capabilities.Has(caps.MessageTags) {
 				continue
 			}
 			user.SendFromClient(msgid, client, clientOnlyTags, "TAGMSG", user.nick)
-			if client.capabilities[caps.EchoMessage] {
+			if client.capabilities.Has(caps.EchoMessage) {
 				client.SendFromClient(msgid, client, clientOnlyTags, "TAGMSG", user.nick)
 			}
 			if user.flags[Away] {
@@ -957,7 +957,7 @@ func tagmsgHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 
 // WhoisChannelsNames returns the common channel names between two users.
 func (client *Client) WhoisChannelsNames(target *Client) []string {
-	isMultiPrefix := target.capabilities[caps.MultiPrefix]
+	isMultiPrefix := target.capabilities.Has(caps.MultiPrefix)
 	var chstrs []string
 	index := 0
 	for channel := range client.channels {
@@ -1062,7 +1062,7 @@ func (target *Client) RplWhoReplyNoMutex(channel *Channel, client *Client) {
 	}
 
 	if channel != nil {
-		flags += channel.members[client].Prefixes(target.capabilities[caps.MultiPrefix])
+		flags += channel.members[client].Prefixes(target.capabilities.Has(caps.MultiPrefix))
 		channelName = channel.name
 	}
 	target.Send(nil, target.server.name, RPL_WHOREPLY, target.nick, channelName, client.username, client.hostname, client.server.name, client.nick, flags, strconv.Itoa(client.hops)+" "+client.realname)
@@ -1288,66 +1288,66 @@ func (server *Server) applyConfig(config *Config, initial bool) error {
 	server.connectionLimitsMutex.Unlock()
 
 	// setup new and removed caps
-	addedCaps := make(CapabilitySet)
-	removedCaps := make(CapabilitySet)
-	updatedCaps := make(CapabilitySet)
+	addedCaps := caps.NewSet()
+	removedCaps := caps.NewSet()
+	updatedCaps := caps.NewSet()
 
 	// SASL
 	if config.Accounts.AuthenticationEnabled && !server.accountAuthenticationEnabled {
 		// enabling SASL
-		SupportedCapabilities[caps.SASL] = true
-		addedCaps[caps.SASL] = true
+		SupportedCapabilities.Enable(caps.SASL)
+		CapValues.Set(caps.SASL, "PLAIN,EXTERNAL")
+		addedCaps.Add(caps.SASL)
 	}
 	if !config.Accounts.AuthenticationEnabled && server.accountAuthenticationEnabled {
 		// disabling SASL
-		SupportedCapabilities[caps.SASL] = false
-		removedCaps[caps.SASL] = true
+		SupportedCapabilities.Disable(caps.SASL)
+		removedCaps.Add(caps.SASL)
 	}
 	server.accountAuthenticationEnabled = config.Accounts.AuthenticationEnabled
 
 	// STS
 	stsValue := config.Server.STS.Value()
 	var stsDisabled bool
-	server.logger.Debug("rehash", "STS Vals", CapValues[caps.STS], stsValue, fmt.Sprintf("server[%v] config[%v]", server.stsEnabled, config.Server.STS.Enabled))
+	stsCurrentCapValue, _ := CapValues.Get(caps.STS)
+	server.logger.Debug("rehash", "STS Vals", stsCurrentCapValue, stsValue, fmt.Sprintf("server[%v] config[%v]", server.stsEnabled, config.Server.STS.Enabled))
 	if config.Server.STS.Enabled && !server.stsEnabled {
 		// enabling STS
-		SupportedCapabilities[caps.STS] = true
-		addedCaps[caps.STS] = true
-		CapValues[caps.STS] = stsValue
+		SupportedCapabilities.Enable(caps.STS)
+		addedCaps.Add(caps.STS)
+		CapValues.Set(caps.STS, stsValue)
 	} else if !config.Server.STS.Enabled && server.stsEnabled {
 		// disabling STS
-		SupportedCapabilities[caps.STS] = false
-		removedCaps[caps.STS] = true
+		SupportedCapabilities.Disable(caps.STS)
+		removedCaps.Add(caps.STS)
 		stsDisabled = true
-	} else if config.Server.STS.Enabled && server.stsEnabled && stsValue != CapValues[caps.STS] {
+	} else if config.Server.STS.Enabled && server.stsEnabled && stsValue != stsCurrentCapValue {
 		// STS policy updated
-		CapValues[caps.STS] = stsValue
-		updatedCaps[caps.STS] = true
+		CapValues.Set(caps.STS, stsValue)
+		updatedCaps.Add(caps.STS)
 	}
 	server.stsEnabled = config.Server.STS.Enabled
 
 	// burst new and removed caps
 	var capBurstClients ClientSet
-	added := make(map[CapVersion]string)
+	added := make(map[caps.Version]string)
 	var removed string
 
 	// updated caps get DEL'd and then NEW'd
 	// so, we can just add updated ones to both removed and added lists here and they'll be correctly handled
-	server.logger.Debug("rehash", "Updated Caps", updatedCaps.String(Cap301), strconv.Itoa(len(updatedCaps)))
-	if len(updatedCaps) > 0 {
-		for capab := range updatedCaps {
-			addedCaps[capab] = true
-			removedCaps[capab] = true
-		}
+	server.logger.Debug("rehash", "Updated Caps", updatedCaps.String(caps.Cap301, CapValues), strconv.Itoa(updatedCaps.Count()))
+	for _, capab := range updatedCaps.List() {
+		addedCaps.Enable(capab)
+		removedCaps.Enable(capab)
 	}
 
-	if len(addedCaps) > 0 || len(removedCaps) > 0 {
+	if 0 < addedCaps.Count() || 0 < removedCaps.Count() {
 		capBurstClients = server.clients.AllWithCaps(caps.CapNotify)
 
-		added[Cap301] = addedCaps.String(Cap301)
-		added[Cap302] = addedCaps.String(Cap302)
-		// removed never has values
-		removed = removedCaps.String(Cap301)
+		added[caps.Cap301] = addedCaps.String(caps.Cap301, CapValues)
+		added[caps.Cap302] = addedCaps.String(caps.Cap302, CapValues)
+		// removed never has values, so we leave it as Cap301
+		removed = removedCaps.String(caps.Cap301, CapValues)
 	}
 
 	for sClient := range capBurstClients {
@@ -1355,18 +1355,18 @@ func (server *Server) applyConfig(config *Config, initial bool) error {
 			// remove STS policy
 			//TODO(dan): this is an ugly hack. we can write this better.
 			stsPolicy := "sts=duration=0"
-			if len(addedCaps) > 0 {
-				added[Cap302] = added[Cap302] + " " + stsPolicy
+			if 0 < addedCaps.Count() {
+				added[caps.Cap302] = added[caps.Cap302] + " " + stsPolicy
 			} else {
-				addedCaps[caps.STS] = true
-				added[Cap302] = stsPolicy
+				addedCaps.Enable(caps.STS)
+				added[caps.Cap302] = stsPolicy
 			}
 		}
 		// DEL caps and then send NEW ones so that updated caps get removed/added correctly
-		if len(removedCaps) > 0 {
+		if 0 < removedCaps.Count() {
 			sClient.Send(nil, server.name, "CAP", sClient.nick, "DEL", removed)
 		}
-		if len(addedCaps) > 0 {
+		if 0 < addedCaps.Count() {
 			sClient.Send(nil, server.name, "CAP", sClient.nick, "NEW", added[sClient.capVersion])
 		}
 	}
@@ -1707,7 +1707,7 @@ func noticeHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 	message := msg.Params[1]
 
 	// split privmsg
-	splitMsg := server.splitMessage(message, !client.capabilities[caps.MaxLine])
+	splitMsg := server.splitMessage(message, !client.capabilities.Has(caps.MaxLine))
 
 	for i, targetString := range targets {
 		// max of four targets per privmsg
@@ -1748,7 +1748,7 @@ func noticeHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 				// errors silently ignored with NOTICE as per RFC
 				continue
 			}
-			if !user.capabilities[caps.MessageTags] {
+			if !user.capabilities.Has(caps.MessageTags) {
 				clientOnlyTags = nil
 			}
 			msgid := server.generateMessageID()
@@ -1757,7 +1757,7 @@ func noticeHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 			if !user.flags[RegisteredOnly] || client.registered {
 				user.SendSplitMsgFromClient(msgid, client, clientOnlyTags, "NOTICE", user.nick, splitMsg)
 			}
-			if client.capabilities[caps.EchoMessage] {
+			if client.capabilities.Has(caps.EchoMessage) {
 				client.SendSplitMsgFromClient(msgid, client, clientOnlyTags, "NOTICE", user.nick, splitMsg)
 			}
 		}