diff --git a/ext/bg/background.html b/ext/bg/background.html
index 2f3fd441..57871242 100644
--- a/ext/bg/background.html
+++ b/ext/bg/background.html
@@ -38,7 +38,6 @@
         <script src="/bg/js/simple-dom-parser.js"></script>
         <script src="/bg/js/text-source-map.js"></script>
         <script src="/bg/js/translator.js"></script>
-        <script src="/bg/js/util.js"></script>
         <script src="/mixed/js/cache-map.js"></script>
         <script src="/mixed/js/audio-system.js"></script>
         <script src="/mixed/js/dictionary-data-util.js"></script>
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index ceb1e257..54982098 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -80,7 +80,6 @@ class Backend {
             ['requestBackendReadySignal',    {async: false, contentScript: true,  handler: this._onApiRequestBackendReadySignal.bind(this)}],
             ['optionsGet',                   {async: false, contentScript: true,  handler: this._onApiOptionsGet.bind(this)}],
             ['optionsGetFull',               {async: false, contentScript: true,  handler: this._onApiOptionsGetFull.bind(this)}],
-            ['optionsSave',                  {async: true,  contentScript: true,  handler: this._onApiOptionsSave.bind(this)}],
             ['kanjiFind',                    {async: true,  contentScript: true,  handler: this._onApiKanjiFind.bind(this)}],
             ['termsFind',                    {async: true,  contentScript: true,  handler: this._onApiTermsFind.bind(this)}],
             ['textParse',                    {async: true,  contentScript: true,  handler: this._onApiTextParse.bind(this)}],
@@ -377,13 +376,6 @@ class Backend {
         return this.getFullOptions();
     }
 
-    async _onApiOptionsSave({source}) {
-        this._clearProfileConditionsSchemaCache();
-        const options = this.getFullOptions();
-        await this._optionsUtil.save(options);
-        this._applyOptions(source);
-    }
-
     async _onApiKanjiFind({text, optionsContext}) {
         const options = this.getOptions(optionsContext);
         const definitions = await this._translator.findKanji(text, options);
@@ -766,7 +758,7 @@ class Backend {
                 results.push({error: errorToJson(e)});
             }
         }
-        await this._onApiOptionsSave({source});
+        await this._saveOptions(source);
         return results;
     }
 
@@ -786,7 +778,7 @@ class Backend {
     async _onApiSetAllSettings({value, source}) {
         this._optionsUtil.validate(value);
         this._options = clone(value);
-        await this._onApiOptionsSave({source});
+        await this._saveOptions(source);
     }
 
     async _onApiGetOrCreateSearchPopup({focus=false, text=null}) {
@@ -879,7 +871,7 @@ class Backend {
         const source = 'popup';
         const options = this.getOptions({current: true});
         options.general.enable = !options.general.enable;
-        await this._onApiOptionsSave({source});
+        await this._saveOptions(source);
     }
 
     // Utilities
@@ -1731,4 +1723,11 @@ class Backend {
     _triggerDatabaseUpdated(type, cause) {
         this._sendMessageAllTabs('databaseUpdated', {type, cause});
     }
+
+    async _saveOptions(source) {
+        this._clearProfileConditionsSchemaCache();
+        const options = this.getFullOptions();
+        await this._optionsUtil.save(options);
+        this._applyOptions(source);
+    }
 }
diff --git a/ext/bg/js/background-main.js b/ext/bg/js/background-main.js
index 1b6bd138..6b64ad37 100644
--- a/ext/bg/js/background-main.js
+++ b/ext/bg/js/background-main.js
@@ -21,8 +21,5 @@
 
 (() => {
     const backend = new Backend();
-    if (typeof window === 'object' && window !== null) {
-        window.yomichanBackend = backend;
-    }
     backend.prepare();
 })();
diff --git a/ext/bg/js/settings/settings-controller.js b/ext/bg/js/settings/settings-controller.js
index 4e61e05c..f4ddf6fb 100644
--- a/ext/bg/js/settings/settings-controller.js
+++ b/ext/bg/js/settings/settings-controller.js
@@ -17,8 +17,6 @@
 
 /* global
  * api
- * utilBackend
- * utilBackgroundIsolate
  */
 
 class SettingsController extends EventDispatcher {
@@ -51,10 +49,6 @@ class SettingsController extends EventDispatcher {
         await this._onOptionsUpdatedInternal();
     }
 
-    async save() {
-        await api.optionsSave(this._source);
-    }
-
     async getOptions() {
         const optionsContext = this.getOptionsContext();
         return await api.optionsGet(optionsContext);
@@ -64,15 +58,6 @@ class SettingsController extends EventDispatcher {
         return await api.optionsGetFull();
     }
 
-    async getOptionsMutable() {
-        const optionsContext = this.getOptionsContext();
-        return utilBackend().getOptions(utilBackgroundIsolate(optionsContext));
-    }
-
-    async getOptionsFullMutable() {
-        return utilBackend().getFullOptions();
-    }
-
     async setAllSettings(value) {
         const profileIndex = value.profileCurrent;
         await api.setAllSettings(value, this._source);
diff --git a/ext/bg/js/util.js b/ext/bg/js/util.js
deleted file mode 100644
index a0f31653..00000000
--- a/ext/bg/js/util.js
+++ /dev/null
@@ -1,29 +0,0 @@
-/*
- * Copyright (C) 2016-2020  Yomichan Authors
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-function utilBackgroundIsolate(data) {
-    const backgroundPage = chrome.extension.getBackgroundPage();
-    return backgroundPage.clone(data);
-}
-
-function utilBackend() {
-    const backend = chrome.extension.getBackgroundPage().yomichanBackend;
-    if (!backend.isPrepared()) {
-        throw new Error('Backend not ready yet');
-    }
-    return backend;
-}
diff --git a/ext/bg/settings.html b/ext/bg/settings.html
index f46282e5..208f3d3f 100644
--- a/ext/bg/settings.html
+++ b/ext/bg/settings.html
@@ -1209,7 +1209,6 @@
         <script src="/bg/js/anki.js"></script>
         <script src="/bg/js/anki-note-builder.js"></script>
         <script src="/bg/js/options.js"></script>
-        <script src="/bg/js/util.js"></script>
         <script src="/bg/js/database.js"></script>
         <script src="/bg/js/dictionary-database.js"></script>
         <script src="/bg/js/dictionary-importer.js"></script>
diff --git a/ext/mixed/js/api.js b/ext/mixed/js/api.js
index ad5846fa..ca4d5732 100644
--- a/ext/mixed/js/api.js
+++ b/ext/mixed/js/api.js
@@ -57,10 +57,6 @@ const api = (() => {
             return this._invoke('optionsGetFull');
         }
 
-        optionsSave(source) {
-            return this._invoke('optionsSave', {source});
-        }
-
         termsFind(text, details, optionsContext) {
             return this._invoke('termsFind', {text, details, optionsContext});
         }
diff --git a/ext/mixed/js/core.js b/ext/mixed/js/core.js
index 8b044a67..351d9371 100644
--- a/ext/mixed/js/core.js
+++ b/ext/mixed/js/core.js
@@ -192,11 +192,6 @@ const clone = (() => {
     return clone;
 })();
 
-// Expose clone function on the global object, since util.js's utilBackgroundIsolate needs access to it.
-if (typeof window === 'object' && window !== null) {
-    window.clone = clone;
-}
-
 function generateId(length) {
     const array = new Uint8Array(length);
     crypto.getRandomValues(array);