diff --git a/src/index.html b/src/index.html
index c710889..3fa0baa 100644
--- a/src/index.html
+++ b/src/index.html
@@ -209,6 +209,7 @@
 		</footer>
 
 		<script src="js/constants.js"></script>
+		<script src="js/strings/en.js"></script>
 		<script src="js/utils.js"></script>
 		<script src="js/validation.js"></script>
 		<script src="js/selection-manager.js"></script>
diff --git a/src/js/auth.js b/src/js/auth.js
index bfa4ad7..b120957 100644
--- a/src/js/auth.js
+++ b/src/js/auth.js
@@ -67,7 +67,7 @@ async function handleLogin() {
 		await initializeApp();
 	} catch (error) {
 		console.error("[Auth] Login failed:", error);
-		ui.authError.textContent = `${MESSAGES.CONNECTION_ERROR} ${error.message}`;
+		ui.authError.textContent = `${STRINGS.CONNECTION_ERROR} ${error.message}`;
 		state.api = null;
 	} finally {
 		handleLogin.isInProgress = false;
diff --git a/src/js/constants.js b/src/js/constants.js
index e383914..0cb6754 100644
--- a/src/js/constants.js
+++ b/src/js/constants.js
@@ -56,13 +56,6 @@ const DOM_IDS = {
 	SECTION_TOGGLE: "section-toggle",
 };
 
-const MESSAGES = {
-	NO_TRACK_PLAYING: "no track playing",
-	NO_ARTISTS: "no artists",
-	NO_PLAYLISTS: "no playlists",
-	CONNECTION_ERROR: "connection failed:",
-};
-
 const ICONS = {
 	PLAY:
 		document.getElementById("icon-play")?.src ||
diff --git a/src/js/library.js b/src/js/library.js
index 07c25dd..d3394cf 100644
--- a/src/js/library.js
+++ b/src/js/library.js
@@ -143,7 +143,7 @@ const TREE_CONFIGS = {
 		data: () => state.library,
 		expandedKey: "artists",
 		expandedMap: () => state.expanded.items.artists,
-		message: MESSAGES.NO_ARTISTS,
+		message: STRINGS.NO_ARTISTS,
 		artType: "artArtist",
 		itemMapper: (artist) => ({
 			label: artist.title || artist.name,
@@ -164,7 +164,7 @@ const TREE_CONFIGS = {
 		data: () => state.playlists,
 		expandedKey: "playlists",
 		expandedMap: () => state.expanded.items.playlists,
-		message: MESSAGES.NO_PLAYLISTS,
+		message: STRINGS.NO_PLAYLISTS,
 		artType: "artArtist",
 		itemMapper: (playlist) => ({
 			label: playlist.name,
diff --git a/src/js/player.js b/src/js/player.js
index 12c5015..a1e0e0e 100644
--- a/src/js/player.js
+++ b/src/js/player.js
@@ -5,8 +5,8 @@ function playTrack(song) {
 		return;
 	}
 
-	ui.trackTitle.textContent = song.title || "Unknown";
-	ui.trackArtist.textContent = song.artist || "Unknown Artist";
+	ui.trackTitle.textContent = song.title || STRINGS.UNKNOWN_TRACK;
+	ui.trackArtist.textContent = song.artist || STRINGS.UNKNOWN_ARTIST;
 	setCoverArt(song);
 	ui.player.src = state.api.getStreamUrl(song.id);
 	ui.player.play();
@@ -67,7 +67,7 @@ function highlightCurrentTrack() {
 // clear player UI and reset to default state
 function clearPlayerUI() {
 	ui.player.src = "";
-	ui.trackTitle.textContent = MESSAGES.NO_TRACK_PLAYING;
+	ui.trackTitle.textContent = STRINGS.NO_TRACK_PLAYING;
 	ui.trackArtist.textContent = "";
 	clearLyrics();
 	ui.coverArt.src = "static/subsonic.png";
@@ -112,8 +112,8 @@ const updateMediaSession = (song) => {
 	if (!song) return;
 	withMediaSession((ms) => {
 		ms.metadata = new MediaMetadata({
-			title: song.title || "Unknown",
-			artist: song.artist || "Unknown Artist",
+			title: song.title || STRINGS.UNKNOWN_TRACK,
+			artist: song.artist || STRINGS.UNKNOWN_ARTIST,
 			album: song.album || "",
 			artwork: song.coverArt
 				? [
diff --git a/src/js/strings/en.js b/src/js/strings/en.js
new file mode 100644
index 0000000..893ff69
--- /dev/null
+++ b/src/js/strings/en.js
@@ -0,0 +1,10 @@
+const STRINGS = {
+	NO_TRACK_PLAYING: "no track playing",
+	NO_ARTISTS: "no artists",
+	NO_PLAYLISTS: "no playlists",
+	CONNECTION_ERROR: "connection failed:",
+	UNKNOWN_TRACK: "unknown",
+	UNKNOWN_ARTIST: "unknown artist",
+	SERVER_URL_EMPTY: "server URL cannot be empty",
+	SERVER_URL_REQUIRED: "server URL is required",
+};
diff --git a/src/js/strings/index.js b/src/js/strings/index.js
new file mode 100644
index 0000000..5ce2609
--- /dev/null
+++ b/src/js/strings/index.js
@@ -0,0 +1,2 @@
+// TODO: add language support
+export { STRINGS } from "./en.js";
diff --git a/src/js/validation.js b/src/js/validation.js
index c3ac16d..df911e5 100644
--- a/src/js/validation.js
+++ b/src/js/validation.js
@@ -14,12 +14,12 @@ function validateId(value, fieldName = "ID") {
 // validate server URL is valid HTTP(S) format
 function validateServerUrl(url) {
 	if (!url || typeof url !== "string") {
-		return buildValidation(false, null, "Server URL is required");
+		return buildValidation(false, null, STRINGS.SERVER_URL_REQUIRED);
 	}
 
 	const trimmed = url.trim();
 	if (!trimmed) {
-		return buildValidation(false, null, "Server URL cannot be empty");
+		return buildValidation(false, null, STRINGS.SERVER_URL_EMPTY);
 	}
 
 	try {