diff --git a/app/ui.js b/app/ui.js
index 71933af6..39d28a33 100644
--- a/app/ui.js
+++ b/app/ui.js
@@ -20,8 +20,12 @@ import * as WebUtil from "./webutil.js";
 
 const PAGE_TITLE = "noVNC";
 
+const LINGUAS = ["cs", "de", "el", "es", "fr", "it", "ja", "ko", "nl", "pl", "pt_BR", "ru", "sv", "tr", "zh_CN", "zh_TW"];
+
 const UI = {
 
+    customSettings: {},
+
     connected: false,
     desktopName: "",
 
@@ -42,20 +46,31 @@ const UI = {
     reconnectCallback: null,
     reconnectPassword: null,
 
-    prime() {
-        return WebUtil.initSettings().then(() => {
-            if (document.readyState === "interactive" || document.readyState === "complete") {
-                return UI.start();
-            }
+    async start(options={}) {
+        UI.customSettings = options.settings || {};
+        if (UI.customSettings.defaults === undefined) {
+            UI.customSettings.defaults = {};
+        }
+        if (UI.customSettings.mandatory === undefined) {
+            UI.customSettings.mandatory = {};
+        }
 
-            return new Promise((resolve, reject) => {
-                document.addEventListener('DOMContentLoaded', () => UI.start().then(resolve).catch(reject));
+        // Set up translations
+        try {
+            await l10n.setup(LINGUAS, "app/locale/");
+        } catch (err) {
+            Log.Error("Failed to load translations: " + err);
+        }
+
+        // Initialize setting storage
+        await WebUtil.initSettings();
+
+        // Wait for the page to load
+        if (document.readyState !== "interactive" && document.readyState !== "complete") {
+            await new Promise((resolve, reject) => {
+                document.addEventListener('DOMContentLoaded', resolve);
             });
-        });
-    },
-
-    // Render default UI and initialize settings menu
-    start() {
+        }
 
         UI.initSettings();
 
@@ -70,22 +85,20 @@ const UI = {
         }
 
         // Try to fetch version number
-        fetch('./package.json')
-            .then((response) => {
-                if (!response.ok) {
-                    throw Error("" + response.status + " " + response.statusText);
-                }
-                return response.json();
-            })
-            .then((packageInfo) => {
-                Array.from(document.getElementsByClassName('noVNC_version')).forEach(el => el.innerText = packageInfo.version);
-            })
-            .catch((err) => {
-                Log.Error("Couldn't fetch package.json: " + err);
-                Array.from(document.getElementsByClassName('noVNC_version_wrapper'))
-                    .concat(Array.from(document.getElementsByClassName('noVNC_version_separator')))
-                    .forEach(el => el.style.display = 'none');
-            });
+        try {
+            let response = await fetch('./package.json');
+            if (!response.ok) {
+                throw Error("" + response.status + " " + response.statusText);
+            }
+
+            let packageInfo = await response.json();
+            Array.from(document.getElementsByClassName('noVNC_version')).forEach(el => el.innerText = packageInfo.version);
+        } catch (err) {
+            Log.Error("Couldn't fetch package.json: " + err);
+            Array.from(document.getElementsByClassName('noVNC_version_wrapper'))
+                .concat(Array.from(document.getElementsByClassName('noVNC_version_separator')))
+                .forEach(el => el.style.display = 'none');
+        }
 
         // Adapt the interface for touch screen devices
         if (isTouchDevice) {
@@ -120,7 +133,7 @@ const UI = {
 
         document.documentElement.classList.remove("noVNC_loading");
 
-        let autoconnect = WebUtil.getConfigVar('autoconnect', false);
+        let autoconnect = UI.getSetting('autoconnect');
         if (autoconnect === 'true' || autoconnect == '1') {
             autoconnect = true;
             UI.connect();
@@ -129,8 +142,6 @@ const UI = {
             // Show the connect panel on first load unless autoconnecting
             UI.openConnectPanel();
         }
-
-        return Promise.resolve(UI.rfb);
     },
 
     initFullscreen() {
@@ -158,23 +169,26 @@ const UI = {
         UI.initSetting('logging', 'warn');
         UI.updateLogging();
 
+        UI.setupSettingLabels();
+
         /* Populate the controls if defaults are provided in the URL */
         UI.initSetting('host', '');
         UI.initSetting('port', 0);
         UI.initSetting('encrypt', (window.location.protocol === "https:"));
+        UI.initSetting('password');
+        UI.initSetting('autoconnect', false);
         UI.initSetting('view_clip', false);
         UI.initSetting('resize', 'off');
         UI.initSetting('quality', 6);
         UI.initSetting('compression', 2);
         UI.initSetting('shared', true);
+        UI.initSetting('bell', 'on');
         UI.initSetting('view_only', false);
         UI.initSetting('show_dot', false);
         UI.initSetting('path', 'websockify');
         UI.initSetting('repeaterID', '');
         UI.initSetting('reconnect', false);
         UI.initSetting('reconnect_delay', 5000);
-
-        UI.setupSettingLabels();
     },
     // Adds a link to the label elements on the corresponding input elements
     setupSettingLabels() {
@@ -736,6 +750,10 @@ const UI = {
 
     // Initial page load read/initialization of settings
     initSetting(name, defVal) {
+        // Has the user overridden the default value?
+        if (name in UI.customSettings.defaults) {
+            defVal = UI.customSettings.defaults[name];
+        }
         // Check Query string followed by cookie
         let val = WebUtil.getConfigVar(name);
         if (val === null) {
@@ -743,6 +761,11 @@ const UI = {
         }
         WebUtil.setSetting(name, val);
         UI.updateSetting(name);
+        // Has the user forced a value?
+        if (name in UI.customSettings.mandatory) {
+            val = UI.customSettings.mandatory[name];
+            UI.forceSetting(name, val);
+        }
         return val;
     },
 
@@ -761,9 +784,12 @@ const UI = {
         let value = UI.getSetting(name);
 
         const ctrl = document.getElementById('noVNC_setting_' + name);
+        if (ctrl === null) {
+            return;
+        }
+
         if (ctrl.type === 'checkbox') {
             ctrl.checked = value;
-
         } else if (typeof ctrl.options !== 'undefined') {
             for (let i = 0; i < ctrl.options.length; i += 1) {
                 if (ctrl.options[i].value === value) {
@@ -796,7 +822,8 @@ const UI = {
     getSetting(name) {
         const ctrl = document.getElementById('noVNC_setting_' + name);
         let val = WebUtil.readSetting(name);
-        if (typeof val !== 'undefined' && val !== null && ctrl.type === 'checkbox') {
+        if (typeof val !== 'undefined' && val !== null &&
+            ctrl !== null && ctrl.type === 'checkbox') {
             if (val.toString().toLowerCase() in {'0': 1, 'no': 1, 'false': 1}) {
                 val = false;
             } else {
@@ -811,14 +838,22 @@ const UI = {
     // disable the labels that belong to disabled input elements.
     disableSetting(name) {
         const ctrl = document.getElementById('noVNC_setting_' + name);
-        ctrl.disabled = true;
-        ctrl.label.classList.add('noVNC_disabled');
+        if (ctrl !== null) {
+            ctrl.disabled = true;
+            if (ctrl.label !== undefined) {
+                ctrl.label.classList.add('noVNC_disabled');
+            }
+        }
     },
 
     enableSetting(name) {
         const ctrl = document.getElementById('noVNC_setting_' + name);
-        ctrl.disabled = false;
-        ctrl.label.classList.remove('noVNC_disabled');
+        if (ctrl !== null) {
+            ctrl.disabled = false;
+            if (ctrl.label !== undefined) {
+                ctrl.label.classList.remove('noVNC_disabled');
+            }
+        }
     },
 
 /* ------^-------
@@ -1000,7 +1035,7 @@ const UI = {
         const path = UI.getSetting('path');
 
         if (typeof password === 'undefined') {
-            password = WebUtil.getConfigVar('password');
+            password = UI.getSetting('password');
             UI.reconnectPassword = password;
         }
 
@@ -1730,7 +1765,7 @@ const UI = {
     },
 
     bell(e) {
-        if (WebUtil.getConfigVar('bell', 'on') === 'on') {
+        if (UI.getSetting('bell') === 'on') {
             const promise = document.getElementById('noVNC_bell').play();
             // The standards disagree on the return value here
             if (promise) {
@@ -1761,10 +1796,4 @@ const UI = {
  */
 };
 
-// Set up translations
-const LINGUAS = ["cs", "de", "el", "es", "fr", "it", "ja", "ko", "nl", "pl", "pt_BR", "ru", "sv", "tr", "zh_CN", "zh_TW"];
-l10n.setup(LINGUAS, "app/locale/")
-    .catch(err => Log.Error("Failed to load translations: " + err))
-    .then(UI.prime);
-
 export default UI;
diff --git a/defaults.json b/defaults.json
new file mode 100644
index 00000000..0967ef42
--- /dev/null
+++ b/defaults.json
@@ -0,0 +1 @@
+{}
diff --git a/mandatory.json b/mandatory.json
new file mode 100644
index 00000000..0967ef42
--- /dev/null
+++ b/mandatory.json
@@ -0,0 +1 @@
+{}
diff --git a/vnc.html b/vnc.html
index 89ee11e3..fd887730 100644
--- a/vnc.html
+++ b/vnc.html
@@ -46,7 +46,56 @@
     <link rel="preload" as="image" href="app/images/warning.svg">
 
     <script type="module" crossorigin="anonymous" src="app/error-handler.js"></script>
-    <script type="module" crossorigin="anonymous" src="app/ui.js"></script>
+
+    <script type="module">
+        import UI from "./app/ui.js";
+        import * as Log from './core/util/logging.js';
+
+        let response;
+
+        let defaults = {};
+        let mandatory = {};
+
+        // Default settings will be loaded from defaults.json. Mandatory
+        // settings will be loaded from mandatory.json, which the user
+        // cannot change.
+
+        try {
+            response = await fetch('./defaults.json');
+            if (!response.ok) {
+                throw Error("" + response.status + " " + response.statusText);
+            }
+
+            defaults = await response.json();
+        } catch (err) {
+            Log.Error("Couldn't fetch defaults.json: " + err);
+        }
+
+        try {
+            response = await fetch('./mandatory.json');
+            if (!response.ok) {
+                throw Error("" + response.status + " " + response.statusText);
+            }
+
+            mandatory = await response.json();
+        } catch (err) {
+            Log.Error("Couldn't fetch mandatory.json: " + err);
+        }
+
+        // You can also override any defaults you need here:
+        //
+        // defaults['host'] = 'vnc.example.com';
+
+        // Or force a specific setting, preventing the user from
+        // changing it:
+        //
+        // mandatory['view_only'] = true;
+
+        // See docs/EMBEDDING.md for a list of possible settings.
+
+        UI.start({ settings: { defaults: defaults,
+                               mandatory: mandatory } });
+    </script>
 </head>
 
 <body>