diff --git a/components/app.js b/components/app.js
index c746ebe..5337d58 100644
--- a/components/app.js
+++ b/components/app.js
@@ -5,12 +5,7 @@ import BufferList from "/components/buffer-list.js";
 import Connect from "/components/connect.js";
 import Composer from "/components/composer.js";
 import { html, Component, createRef } from "/lib/index.js";
-
-const SERVER_BUFFER = "*";
-
-const DISCONNECTED = "disconnected";
-const CONNECTING = "connecting";
-const REGISTERED = "registered";
+import { SERVER_BUFFER, Status, Unread } from "/state.js";
 
 function parseQueryString() {
 	var query = window.location.search.substring(1);
@@ -37,7 +32,7 @@ export default class App extends Component {
 			saslPlain: null,
 			autojoin: [],
 		},
-		status: DISCONNECTED,
+		status: Status.DISCONNECTED,
 		buffers: new Map(),
 		activeBuffer: null,
 	};
@@ -58,7 +53,12 @@ export default class App extends Component {
 				return;
 			}
 
-			var updated = updater(buf);
+			var updated;
+			if (typeof updater === "function") {
+				updated = updater(buf, state);
+			} else {
+				updated = updater;
+			}
 			if (buf === updated || !updated) {
 				return;
 			}
@@ -82,12 +82,14 @@ export default class App extends Component {
 				topic: null,
 				members: new Map(),
 				messages: [],
+				unread: Unread.NONE,
 			});
 			return { buffers };
 		});
 	}
 
 	switchBuffer(name) {
+		this.setBufferState(name, { unread: Unread.NONE });
 		this.setState({ activeBuffer: name }, () => {
 			if (this.composer.current) {
 				this.composer.current.focus();
@@ -101,14 +103,26 @@ export default class App extends Component {
 		}
 		// TODO: set time tag if missing
 
+		var unread = Unread.NONE;
+		if (msg.command == "PRIVMSG" || msg.command == "NOTICE") {
+			unread = Unread.MESSAGE;
+		}
+
 		this.createBuffer(bufName);
-		this.setBufferState(bufName, (buf) => {
-			return { messages: buf.messages.concat(msg) };
+		this.setBufferState(bufName, (buf, state) => {
+			var unread = buf.unread;
+			if (state.activeBuffer != buf.name) {
+				unread = Unread.union(buf.unread, unread);
+			}
+			return {
+				messages: buf.messages.concat(msg),
+				unread,
+			};
 		});
 	}
 
 	connect(params) {
-		this.setState({ status: CONNECTING, connectParams: params });
+		this.setState({ status: Status.CONNECTING, connectParams: params });
 
 		this.client = new Client({
 			url: params.serverURL,
@@ -121,7 +135,7 @@ export default class App extends Component {
 
 		this.client.addEventListener("close", () => {
 			this.setState({
-				status: DISCONNECTED,
+				status: Status.DISCONNECTED,
 				buffers: new Map(),
 				activeBuffer: null,
 			});
@@ -138,7 +152,7 @@ export default class App extends Component {
 	handleMessage(msg) {
 		switch (msg.command) {
 		case irc.RPL_WELCOME:
-			this.setState({ status: REGISTERED });
+			this.setState({ status: Status.REGISTERED });
 
 			if (this.state.connectParams.autojoin.length > 0) {
 				this.client.send({
@@ -151,9 +165,7 @@ export default class App extends Component {
 			var channel = msg.params[1];
 			var topic = msg.params[2];
 
-			this.setBufferState(channel, (buf) => {
-				return { topic };
-			});
+			this.setBufferState(channel, { topic });
 			break;
 		case irc.RPL_NAMREPLY:
 			var channel = msg.params[2];
@@ -230,9 +242,7 @@ export default class App extends Component {
 			var channel = msg.params[0];
 			var topic = msg.params[1];
 
-			this.setBufferState(channel, (buf) => {
-				return { topic };
-			});
+			this.setBufferState(channel, { topic });
 			this.addMessage(channel, msg);
 			break;
 		default:
@@ -377,10 +387,10 @@ export default class App extends Component {
 	}
 
 	render() {
-		if (this.state.status != REGISTERED) {
+		if (this.state.status != Status.REGISTERED) {
 			return html`
 				<section id="connect">
-					<${Connect} params=${this.state.connectParams} disabled=${this.state.status != DISCONNECTED} onSubmit=${this.handleConnectSubmit}/>
+					<${Connect} params=${this.state.connectParams} disabled=${this.state.status != Status.DISCONNECTED} onSubmit=${this.handleConnectSubmit}/>
 				</section>
 			`;
 		}
diff --git a/components/buffer-list.js b/components/buffer-list.js
index 8b455c0..45f665e 100644
--- a/components/buffer-list.js
+++ b/components/buffer-list.js
@@ -1,4 +1,5 @@
 import { html, Component } from "/lib/index.js";
+import { SERVER_BUFFER, Unread } from "/state.js";
 
 function BufferItem(props) {
 	function handleClick(event) {
@@ -7,12 +8,19 @@ function BufferItem(props) {
 	}
 
 	var name = props.buffer.name;
-	if (name == "*") {
+	if (name == SERVER_BUFFER) {
 		name = "server";
 	}
 
+	var activeClass = props.active ? "active" : "";
+
+	var unreadClass = "";
+	if (props.buffer.unread != Unread.NONE) {
+		unreadClass = "unread-" + props.buffer.unread;
+	}
+
 	return html`
-		<li class=${props.active ? "active" : ""}>
+		<li class="${activeClass} ${unreadClass}">
 			<a href="#" onClick=${handleClick}>${name}</a>
 		</li>
 	`;
diff --git a/state.js b/state.js
new file mode 100644
index 0000000..4b32105
--- /dev/null
+++ b/state.js
@@ -0,0 +1,20 @@
+export const SERVER_BUFFER = "*";
+
+export const Status = {
+	DISCONNECTED: "disconnected",
+	CONNECTING: "connecting",
+	REGISTERED: "registered",
+};
+
+export const Unread = {
+	NONE: "",
+	MESSAGE: "message",
+
+	union: (a, b) => {
+		const priority = {
+			[Unread.None]: 0,
+			[Unread.MESSAGE]: 1,
+		};
+		return (priority[a] > priority[b]) ? a : b;
+	},
+};
diff --git a/style.css b/style.css
index 27c9a78..07bbb7c 100644
--- a/style.css
+++ b/style.css
@@ -79,6 +79,9 @@ a {
 #sidebar .active a {
 	color: black;
 }
+#sidebar .unread-message a {
+	font-weight: bold;
+}
 #sidebar a:hover, #sidebar a:active,
 a.timestamp:hover, a.timestamp:active,
 a.nick:hover, a.nick:active {