diff --git a/README.md b/README.md
index e913535..34944a8 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,8 @@ The server will be available at `ws://localhost:3000`. See [docker-compose.examp
 
 To connect your extension to a self-hosted server, open the popup → **Room** tab → select **Custom Server** → enter your server's WebSocket URL (e.g., `ws://localhost:3000`).
 
+> **⚠️ Note**: `ws://` only works for `localhost`. If you deploy to a real domain, you **must** use `wss://` (e.g., `wss://sync.yourdomain.com`). This requires a TLS-terminating reverse proxy (e.g., Caddy, Nginx, or Traefik) in front of the relay server.
+
 ---
 
 ### 📖 Documentation & Links