diff --git a/background/background.js b/background/background.js
index e4d958c1..634559f2 100644
--- a/background/background.js
+++ b/background/background.js
@@ -153,6 +153,14 @@ navigatorUtil.onUrlChange(({url, tabId, frameId}) => {
   }
 });
 
+prefs.subscribe([
+  'show-badge',
+  'disableAll',
+  'badgeDisabled',
+  'badgeNormal',
+  'iconset',
+], () => debounce(updateAllTabsIcon));
+
 // *************************************************************************
 chrome.runtime.onInstalled.addListener(({reason}) => {
   if (reason !== 'update') return;
@@ -211,11 +219,10 @@ if (chrome.contextMenus) {
       }
       item = Object.assign({id}, item);
       delete item.presentIf;
-      const prefValue = prefs.readOnlyValues[id];
       item.title = chrome.i18n.getMessage(item.title);
-      if (!item.type && typeof prefValue === 'boolean') {
+      if (!item.type && typeof prefs.defaults[id] === 'boolean') {
         item.type = 'checkbox';
-        item.checked = prefValue;
+        item.checked = prefs.get(id);
       }
       if (!item.contexts) {
         item.contexts = ['browser_action'];
@@ -239,7 +246,7 @@ if (chrome.contextMenus) {
   };
 
   const keys = Object.keys(contextMenus);
-  prefs.subscribe(keys.filter(id => typeof prefs.readOnlyValues[id] === 'boolean'), toggleCheckmark);
+  prefs.subscribe(keys.filter(id => typeof prefs.defaults[id] === 'boolean'), toggleCheckmark);
   prefs.subscribe(keys.filter(id => contextMenus[id].presentIf), togglePresence);
   createContextMenus(keys);
 }
@@ -307,6 +314,21 @@ window.addEventListener('storageReady', function _() {
 
 // FIXME: implement exposeIframes in apply.js
 
+// register hotkeys
+if (FIREFOX && browser.commands && browser.commands.update) {
+  const hotkeyPrefs = Object.keys(prefs.defaults).filter(k => k.startsWith('hotkey.'));
+  prefs.subscribe(hotkeyPrefs, (name, value) => {
+    try {
+      name = name.split('.')[1];
+      if (value.trim()) {
+        browser.commands.update({name, shortcut: value});
+      } else {
+        browser.commands.reset(name);
+      }
+    } catch (e) {}
+  });
+}
+
 function webNavUsercssInstallerFF(data) {
   const {tabId} = data;
   Promise.all([
@@ -447,3 +469,9 @@ function onRuntimeMessage(msg, sender) {
   const context = {msg, sender};
   return fn.apply(context, msg.args);
 }
+
+function updateAllTabsIcon() {
+  return queryTabs().then(tabs =>
+    tabs.map(t => updateIcon({tab: t}))
+  );
+}
diff --git a/content/apply.js b/content/apply.js
index 8a229661..9bd701bc 100644
--- a/content/apply.js
+++ b/content/apply.js
@@ -48,6 +48,10 @@
     window.addEventListener(chrome.runtime.id, orphanCheck, true);
   }
 
+  // FIXME: does it work with styleViaAPI?
+  prefs.subscribe(['disableAll'], (key, value) => doDisableAll(value));
+  prefs.subscribe(['exposeIframes'], (key, value) => doExposeIframes(value));
+
   function getMatchUrl() {
     var matchUrl = location.href;
     if (!matchUrl.match(/^(http|file|chrome|ftp)/)) {
@@ -135,7 +139,6 @@
         break;
 
       case 'urlChanged':
-        console.log('url changed', location.href);
         API.getSectionsByUrl(getMatchUrl(), {enabled: true})
           .then(buildSections)
           .then(replaceAll);
diff --git a/edit/edit.js b/edit/edit.js
index 13d8daee..9420d1c3 100644
--- a/edit/edit.js
+++ b/edit/edit.js
@@ -238,6 +238,9 @@ preinit();
   }
 })();
 
+prefs.subscribe(['editor.smartIndent'], (key, value) =>
+  CodeMirror.setOption('smartIndent', value));
+
 function preinit() {
   // make querySelectorAll enumeration code readable
   // FIXME: don't extend native
diff --git a/js/dom.js b/js/dom.js
index c956d729..7ffb9ce6 100644
--- a/js/dom.js
+++ b/js/dom.js
@@ -392,3 +392,55 @@ function moveFocus(rootElement, step) {
     }
   }
 }
+
+// Accepts an array of pref names (values are fetched via prefs.get)
+// and establishes a two-way connection between the document elements and the actual prefs
+function setupLivePrefs(
+  IDs = Object.getOwnPropertyNames(prefs.defaults)
+    .filter(id => $('#' + id))
+) {
+  for (const id of IDs) {
+    const element = $('#' + id);
+    updateElement({id, element, force: true});
+    element.addEventListener('change', onChange);
+  }
+  prefs.subscribe(IDs, (id, value) => updateElement({id, value}));
+
+  function onChange() {
+    const value = getInputValue(this);
+    if (prefs.get(this.id) !== value) {
+      prefs.set(this.id, value);
+    }
+  }
+  function updateElement({
+    id,
+    value = prefs.get(id),
+    element = $('#' + id),
+    force,
+  }) {
+    if (!element) {
+      prefs.unsubscribe(IDs, updateElement);
+      return;
+    }
+    setInputValue(element, value, force);
+  }
+  function getInputValue(input) {
+    if (input.type === 'checkbox') {
+      return input.checked;
+    }
+    if (input.type === 'number') {
+      return Number(input.value);
+    }
+    return input.value;
+  }
+  function setInputValue(input, value, force = false) {
+    if (force || getInputValue(input) !== value) {
+      if (input.type === 'checkbox') {
+        input.checked = value;
+      } else {
+        input.value = value;
+      }
+      input.dispatchEvent(new Event('change', {bubbles: true, cancelable: true}));
+    }
+  }
+}
diff --git a/js/messaging.js b/js/messaging.js
index eb83a738..fc1cb78a 100644
--- a/js/messaging.js
+++ b/js/messaging.js
@@ -91,12 +91,9 @@ if (IS_BG) {
   window.API_METHODS = {};
 }
 
-const FIREFOX_NO_DOM_STORAGE = FIREFOX && !tryCatch(() => localStorage);
-if (FIREFOX_NO_DOM_STORAGE) {
-  // may be disabled via dom.storage.enabled
-  Object.defineProperty(window, 'localStorage', {value: {}});
-  Object.defineProperty(window, 'sessionStorage', {value: {}});
-}
+// FIXME: `localStorage` and `sessionStorage` may be disabled via dom.storage.enabled
+// Object.defineProperty(window, 'localStorage', {value: {}});
+// Object.defineProperty(window, 'sessionStorage', {value: {}});
 
 function queryTabs(options = {}) {
   return new Promise(resolve =>
diff --git a/js/prefs.js b/js/prefs.js
index 32de5bd4..f798a96a 100644
--- a/js/prefs.js
+++ b/js/prefs.js
@@ -2,8 +2,7 @@
 /* exported prefs */
 'use strict';
 
-const prefs = new function Prefs() {
-  const BG = undefined;
+const prefs = (() => {
   const defaults = {
     'openEditInWindow': false,      // new editor opens in a own browser window
     'windowPosition': {},           // detached window position
@@ -99,29 +98,33 @@ const prefs = new function Prefs() {
   };
   const values = deepCopy(defaults);
 
-  const affectsIcon = [
-    'show-badge',
-    'disableAll',
-    'badgeDisabled',
-    'badgeNormal',
-    'iconset',
-  ];
-
   const onChange = {
     any: new Set(),
     specific: new Map(),
   };
 
-  // coalesce multiple pref changes in broadcast
-  let broadcastPrefs = {};
+  const initializing = promisify(chrome.storage.sync.get.bind(chrome.storage.sync))('settings')
+    .then(result => {
+      if (result.settings) {
+        setAll(result.settings, true);
+      }
+    });
 
-  Object.defineProperties(this, {
-    defaults: {value: deepCopy(defaults)},
-    readOnlyValues: {value: {}},
+  chrome.storage.onChanged.addListener((changes, area) => {
+    if (area !== 'sync' || !changes.settings || !changes.settings.newValue) {
+      return;
+    }
+    initializing.then(() => setAll(changes.settings.newValue, true));
   });
 
-  Object.assign(Prefs.prototype, {
+  let timer;
 
+  // coalesce multiple pref changes in broadcast
+  // let changes = {};
+
+  return {
+    initializing,
+    defaults,
     get(key, defaultValue) {
       if (key in values) {
         return values[key];
@@ -134,62 +137,11 @@ const prefs = new function Prefs() {
       }
       console.warn("No default preference for '%s'", key);
     },
-
     getAll() {
       return deepCopy(values);
     },
-
-    set(key, value, {broadcast = true, sync = true, fromBroadcast} = {}) {
-      const oldValue = values[key];
-      switch (typeof defaults[key]) {
-        case typeof value:
-          break;
-        case 'string':
-          value = String(value);
-          break;
-        case 'number':
-          value |= 0;
-          break;
-        case 'boolean':
-          value = value === true || value === 'true';
-          break;
-      }
-      values[key] = value;
-      defineReadonlyProperty(this.readOnlyValues, key, value);
-      const hasChanged = !equal(value, oldValue);
-      if (!fromBroadcast || FIREFOX_NO_DOM_STORAGE) {
-        localStorage[key] = typeof defaults[key] === 'object'
-          ? JSON.stringify(value)
-          : value;
-      }
-      if (!fromBroadcast && broadcast && hasChanged) {
-        this.broadcast(key, value, {sync});
-      }
-      if (hasChanged) {
-        const specific = onChange.specific.get(key);
-        if (typeof specific === 'function') {
-          specific(key, value);
-        } else if (specific instanceof Set) {
-          for (const listener of specific.values()) {
-            listener(key, value);
-          }
-        }
-        for (const listener of onChange.any.values()) {
-          listener(key, value);
-        }
-      }
-    },
-
-    reset: key => this.set(key, deepCopy(defaults[key])),
-
-    broadcast(key, value, {sync = true} = {}) {
-      broadcastPrefs[key] = value;
-      debounce(doBroadcast);
-      if (sync) {
-        debounce(doSyncSet);
-      }
-    },
-
+    set,
+    reset: key => set(key, deepCopy(defaults[key])),
     subscribe(keys, listener) {
       // keys:     string[] ids
       //           or a falsy value to subscribe to everything
@@ -209,7 +161,6 @@ const prefs = new function Prefs() {
         onChange.any.add(listener);
       }
     },
-
     unsubscribe(keys, listener) {
       if (keys) {
         for (const key of keys) {
@@ -227,147 +178,75 @@ const prefs = new function Prefs() {
         onChange.all.remove(listener);
       }
     },
-  });
+  };
 
-  {
-    const importFromBG = () =>
-      API.getPrefs().then(prefs => {
-        const props = {};
-        for (const id in prefs) {
-          const value = prefs[id];
-          values[id] = value;
-          props[id] = {value: deepCopy(value)};
-        }
-        Object.defineProperties(this.readOnlyValues, props);
-      });
-    // Unlike chrome.storage or messaging, HTML5 localStorage is synchronous and always ready,
-    // so we'll mirror the prefs to avoid using the wrong defaults during the startup phase
-    const importFromLocalStorage = () => {
-      forgetOutdatedDefaults(localStorage);
-      for (const key in defaults) {
-        const defaultValue = defaults[key];
-        let value = localStorage[key];
-        if (typeof value === 'string') {
-          switch (typeof defaultValue) {
-            case 'boolean':
-              value = value.toLowerCase() === 'true';
-              break;
-            case 'number':
-              value |= 0;
-              break;
-            case 'object':
-              value = tryJSONparse(value) || defaultValue;
-              break;
+  function promisify(fn) {
+    return (...args) =>
+      new Promise((resolve, reject) => {
+        fn(...args, (...result) => {
+          if (chrome.runtime.lastError) {
+            reject(chrome.runtime.lastError);
+          } else if (result.length === 0) {
+            resolve(undefined);
+          } else if (result.length === 1) {
+            resolve(result[0]);
+          } else {
+            resolve(result);
           }
-        } else if (FIREFOX_NO_DOM_STORAGE && BG) {
-          value = BG.localStorage[key];
-          value = value === undefined ? defaultValue : value;
-          localStorage[key] = value;
-        } else {
-          value = defaultValue;
-        }
-        if (BG === window) {
-          // when in bg page, .set() will write to localStorage
-          this.set(key, value, {broadcast: false, sync: false});
-        } else {
-          values[key] = value;
-          defineReadonlyProperty(this.readOnlyValues, key, value);
-        }
-      }
-      return Promise.resolve();
-    };
-    (FIREFOX_NO_DOM_STORAGE && !BG ? importFromBG() : importFromLocalStorage()).then(() => {
-      if (BG && BG !== window) return;
-      if (BG === window) {
-        affectsIcon.forEach(key => this.broadcast(key, values[key], {sync: false}));
-        chromeSync.getValue('settings').then(settings => importFromSync.call(this, settings));
-      }
-      chrome.storage.onChanged.addListener((changes, area) => {
-        if (area === 'sync' && 'settings' in changes) {
-          importFromSync.call(this, changes.settings.newValue);
-        }
+        });
       });
-    });
   }
 
-  // any access to chrome API takes time due to initialization of bindings
-  window.addEventListener('load', function _() {
-    window.removeEventListener('load', _);
-    chrome.runtime.onMessage.addListener(msg => {
-      if (msg.prefs) {
-        for (const id in msg.prefs) {
-          prefs.set(id, msg.prefs[id], {fromBroadcast: true});
-        }
-      }
-    });
-  });
-
-  // register hotkeys
-  if (FIREFOX && (browser.commands || {}).update) {
-    const hotkeyPrefs = Object.keys(values).filter(k => k.startsWith('hotkey.'));
-    this.subscribe(hotkeyPrefs, (name, value) => {
-      try {
-        name = name.split('.')[1];
-        if (value.trim()) {
-          browser.commands.update({name, shortcut: value}).catch(ignoreChromeError);
-        } else {
-          browser.commands.reset(name).catch(ignoreChromeError);
-        }
-      } catch (e) {}
-    });
-  }
-
-  return;
-
-  function doBroadcast() {
-    // if (BG && BG === window && !BG.dbExec.initialized) {
-      // window.addEventListener('storageReady', function _() {
-        // window.removeEventListener('storageReady', _);
-        // doBroadcast();
-      // });
-      // return;
-    // }
-    const affects = {
-      all: 'disableAll' in broadcastPrefs
-        || 'exposeIframes' in broadcastPrefs,
-    };
-    if (!affects.all) {
-      for (const key in broadcastPrefs) {
-        affects.icon = affects.icon || affectsIcon.includes(key);
-        affects.popup = affects.popup || key.startsWith('popup');
-        affects.editor = affects.editor || key.startsWith('editor');
-        affects.manager = affects.manager || key.startsWith('manage');
-      }
-    }
-    notifyAllTabs({method: 'prefChanged', prefs: broadcastPrefs, affects});
-    broadcastPrefs = {};
-  }
-
-  function doSyncSet() {
-    chromeSync.setValue('settings', values);
-  }
-
-  function importFromSync(synced = {}) {
-    forgetOutdatedDefaults(synced);
-    for (const key in defaults) {
-      if (key in synced) {
-        this.set(key, synced[key], {sync: false});
-      }
+  function setAll(settings, synced) {
+    for (const [key, value] of Object.entries(settings)) {
+      set(key, value, synced);
     }
   }
 
-  function forgetOutdatedDefaults(storage) {
-    // our linter runs as a worker so we can reduce the delay and forget the old default values
-    if (Number(storage['editor.lintDelay']) === 500) delete storage['editor.lintDelay'];
-    if (Number(storage['editor.lintReportDelay']) === 4500) delete storage['editor.lintReportDelay'];
+  function set(key, value, synced = false) {
+    const oldValue = values[key];
+    switch (typeof defaults[key]) {
+      case typeof value:
+        break;
+      case 'string':
+        value = String(value);
+        break;
+      case 'number':
+        value |= 0;
+        break;
+      case 'boolean':
+        value = value === true || value === 'true';
+        break;
+    }
+    if (equal(value, oldValue)) {
+      return;
+    }
+    values[key] = value;
+    emitChange(key, value);
+    if (synced || timer) {
+      return;
+    }
+    timer = setTimeout(syncPrefs);
   }
 
-  function defineReadonlyProperty(obj, key, value) {
-    const copy = deepCopy(value);
-    if (typeof copy === 'object') {
-      Object.freeze(copy);
+  function emitChange(key, value) {
+    const specific = onChange.specific.get(key);
+    if (typeof specific === 'function') {
+      specific(key, value);
+    } else if (specific instanceof Set) {
+      for (const listener of specific.values()) {
+        listener(key, value);
+      }
     }
-    Object.defineProperty(obj, key, {value: copy, configurable: true});
+    for (const listener of onChange.any.values()) {
+      listener(key, value);
+    }
+  }
+
+  function syncPrefs() {
+    // FIXME: we always set the entire object? Ideally, this should only use `changes`.
+    chrome.storage.sync.set({settings: values});
+    timer = null;
   }
 
   function equal(a, b) {
@@ -390,7 +269,7 @@ const prefs = new function Prefs() {
   }
 
   function contextDeleteMissing() {
-    return CHROME && (
+    return /Chrome\/\d+/.test(navigator.userAgent) && (
       // detect browsers without Delete by looking at the end of UA string
       /Vivaldi\/[\d.]+$/.test(navigator.userAgent) ||
       // Chrome and co.
@@ -399,44 +278,17 @@ const prefs = new function Prefs() {
       !Array.from(navigator.plugins).some(p => p.name === 'Shockwave Flash')
     );
   }
-}();
 
-
-// Accepts an array of pref names (values are fetched via prefs.get)
-// and establishes a two-way connection between the document elements and the actual prefs
-function setupLivePrefs(
-  IDs = Object.getOwnPropertyNames(prefs.readOnlyValues)
-    .filter(id => $('#' + id))
-) {
-  const checkedProps = {};
-  for (const id of IDs) {
-    const element = $('#' + id);
-    checkedProps[id] = element.type === 'checkbox' ? 'checked' : 'value';
-    updateElement({id, element, force: true});
-    element.addEventListener('change', onChange);
-  }
-  prefs.subscribe(IDs, (id, value) => updateElement({id, value}));
-
-  function onChange() {
-    const value = this[checkedProps[this.id]];
-    if (prefs.get(this.id) !== value) {
-      prefs.set(this.id, value);
+  function deepCopy(obj) {
+    if (!obj || typeof obj !== 'object') {
+      return obj;
     }
-  }
-  function updateElement({
-    id,
-    value = prefs.get(id),
-    element = $('#' + id),
-    force,
-  }) {
-    if (!element) {
-      prefs.unsubscribe(IDs, updateElement);
-      return;
-    }
-    const prop = checkedProps[id];
-    if (force || element[prop] !== value) {
-      element[prop] = value;
-      element.dispatchEvent(new Event('change', {bubbles: true, cancelable: true}));
+    if (Array.isArray(obj)) {
+      return obj.map(deepCopy);
     }
+    return Object.keys(obj).reduce((output, key) => {
+      output[key] = deepCopy(obj[key]);
+      return output;
+    }, {});
   }
-}
+})();
diff --git a/manage/filters.js b/manage/filters.js
index 007ebc4b..b09c3193 100644
--- a/manage/filters.js
+++ b/manage/filters.js
@@ -114,7 +114,7 @@ onDOMready().then(() => {
       }
       if (value !== undefined) {
         el.lastValue = value;
-        if (el.id in prefs.readOnlyValues) {
+        if (el.id in prefs.defaults) {
           prefs.set(el.id, false);
         }
       }
diff --git a/manage/manage.js b/manage/manage.js
index e3997c25..e13c8865 100644
--- a/manage/manage.js
+++ b/manage/manage.js
@@ -701,8 +701,8 @@ function highlightEditedStyle() {
 
 
 function usePrefsDuringPageLoad() {
-  for (const id of Object.getOwnPropertyNames(prefs.readOnlyValues)) {
-    const value = prefs.readOnlyValues[id];
+  for (const id of Object.getOwnPropertyNames(prefs.defaults)) {
+    const value = prefs.get(id);
     if (value !== true) continue;
     const el = document.getElementById(id) ||
       id.includes('expanded') && $(`details[data-pref="${id}"]`);
diff --git a/manifest.json b/manifest.json
index 671946c2..43b53d94 100644
--- a/manifest.json
+++ b/manifest.json
@@ -62,7 +62,7 @@
       "run_at": "document_start",
       "all_frames": true,
       "match_about_blank": true,
-      "js": ["js/promisify.js", "js/msg.js", "content/apply.js"]
+      "js": ["js/promisify.js", "js/msg.js", "js/prefs.js", "content/apply.js"]
     },
     {
       "matches": ["http://userstyles.org/*", "https://userstyles.org/*"],
@@ -115,5 +115,11 @@
   "options_ui": {
     "page": "options.html",
     "chrome_style": false
+  },
+  "applications": {
+    "gecko": {
+      "id": "{7a7a4a92-a2a0-41d1-9fd7-1e92480d612d}",
+      "strict_min_version": "53"
+    }
   }
 }
diff --git a/options/options.js b/options/options.js
index 2f9d929f..a657589e 100644
--- a/options/options.js
+++ b/options/options.js
@@ -59,7 +59,7 @@ document.onclick = e => {
 
     case 'reset':
       $$('input')
-        .filter(input => input.id in prefs.readOnlyValues)
+        .filter(input => input.id in prefs.defaults)
         .forEach(input => prefs.reset(input.id));
       break;
 
diff --git a/package.json b/package.json
index 1f519203..f0fdf8dc 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,8 @@
     "semver-bundle": "^0.1.1",
     "stylelint-bundle": "^8.0.0",
     "stylus-lang-bundle": "^0.54.5",
-    "updates": "^4.2.1"
+    "updates": "^4.2.1",
+    "web-ext": "^2.9.1"
   },
   "scripts": {
     "lint": "eslint **/*.js --cache || exit 0",
@@ -27,6 +28,7 @@
     "update-node": "updates -u && node tools/remove-modules.js && npm install",
     "update-codemirror": "node tools/update-libraries.js && node tools/update-codemirror-themes.js",
     "update-versions": "node tools/update-versions",
-    "zip": "npm run update-versions && node tools/zip.js"
+    "zip": "npm run update-versions && node tools/zip.js",
+    "start": "web-ext run"
   }
 }
diff --git a/popup/popup.js b/popup/popup.js
index 54702ea0..159739a4 100644
--- a/popup/popup.js
+++ b/popup/popup.js
@@ -31,6 +31,14 @@ getActiveTab().then(tab =>
 
 msg.onExtension(onRuntimeMessage);
 
+prefs.subscribe(['popup.stylesFirst'], (key, stylesFirst) => {
+  const actions = $('body > .actions');
+  const before = stylesFirst ? actions : actions.nextSibling;
+  document.body.insertBefore(installed, before);
+});
+prefs.subscribe(['popupWidth'], (key, value) => setPopupWidth(value));
+prefs.subscribe(['popup.borders'], (key, value) => toggleSideBorders(value));
+
 function onRuntimeMessage(msg) {
   switch (msg.method) {
     case 'styleAdded':
@@ -42,18 +50,6 @@ function onRuntimeMessage(msg) {
     case 'styleDeleted':
       handleDelete(msg.style.id);
       break;
-    case 'prefChanged':
-      if ('popup.stylesFirst' in msg.prefs) {
-        const stylesFirst = msg.prefs['popup.stylesFirst'];
-        const actions = $('body > .actions');
-        const before = stylesFirst ? actions : actions.nextSibling;
-        document.body.insertBefore(installed, before);
-      } else if ('popupWidth' in msg.prefs) {
-        setPopupWidth(msg.prefs.popupWidth);
-      } else if ('popup.borders' in msg.prefs) {
-        toggleSideBorders(msg.prefs['popup.borders']);
-      }
-      break;
   }
   dispatchEvent(new CustomEvent(msg.method, {detail: msg}));
 }