diff --git a/waterfox/browser/components/WaterfoxGlue.jsm b/waterfox/browser/components/WaterfoxGlue.jsm
index 3b24743a19a2..b7be572bca78 100644
--- a/waterfox/browser/components/WaterfoxGlue.jsm
+++ b/waterfox/browser/components/WaterfoxGlue.jsm
@@ -22,7 +22,7 @@ XPCOMUtils.defineLazyModuleGetters(lazy, {
   PrefUtils: "resource:///modules/PrefUtils.jsm",
   PrivateTab: "resource:///modules/PrivateTab.sys.mjs",
   StatusBar: "resource:///modules/StatusBar.sys.mjs",
-  TabFeatures: "resource:///modules/TabFeatures.jsm",
+  TabFeatures: "resource:///modules/TabFeatures.sys.mjs",
   UICustomizations: "resource:///modules/UICustomizations.jsm",
 });
 
diff --git a/waterfox/browser/components/tabfeatures/TabFeatures.jsm b/waterfox/browser/components/tabfeatures/TabFeatures.jsm
deleted file mode 100644
index 81dd51dd46bd..000000000000
--- a/waterfox/browser/components/tabfeatures/TabFeatures.jsm
+++ /dev/null
@@ -1,156 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* global */
-
-const EXPORTED_SYMBOLS = ["TabFeatures"];
-
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-
-const { AppConstants } = ChromeUtils.import(
-  "resource://gre/modules/AppConstants.jsm"
-);
-
-const TabFeatures = {
-  PREF_ACTIVETAB: "browser.tabs.copyurl.activetab",
-  PREF_REQUIRECONFIRM: "browser.restart_menu.requireconfirm",
-  PREF_PURGECACHE: "browser.restart_menu.purgecache",
-
-  init(window) {
-    window.TabFeatures = this;
-    this.initListeners(window);
-  },
-
-  initListeners(aWindow) {
-    aWindow.document
-      .getElementById("tabContextMenu")
-      ?.addEventListener("popupshowing", this.tabContext);
-    if (AppConstants.platform == "macosx") {
-      aWindow.document
-        .getElementById("file-menu")
-        ?.addEventListener("popupshowing", this.tabContext);
-    } else {
-      aWindow.document
-        .getElementById("appMenu-popup")
-        ?.addEventListener("popupshowing", this.tabContext);
-    }
-  },
-
-  tabContext(aEvent) {
-    let win = aEvent.view;
-    if (!win) {
-      win = Services.wm.getMostRecentWindow("navigator:browser");
-    }
-    let { document } = win;
-    let elements = document.getElementsByClassName("tabFeature");
-    for (let i = 0; i < elements.length; i++) {
-      let el = elements[i];
-      let pref = el.getAttribute("preference");
-      if (pref) {
-        let visible = Services.prefs.getBoolPref(pref);
-        el.hidden = !visible;
-      }
-    }
-    // Can't unload selected tab, so don't show menu item in that case
-    if (win.TabContextMenu.contextTab === win.gBrowser.selectedTab) {
-      const el = document.getElementById("context_unloadTab");
-      el.hidden = true;
-    }
-  },
-
-  // Copies current tab url to clipboard
-  copyTabUrl(aUri, aWindow) {
-    const gClipboardHelper = Cc[
-      "@mozilla.org/widget/clipboardhelper;1"
-    ].getService(Ci.nsIClipboardHelper);
-    try {
-      Services.prefs.getBoolPref(this.PREF_ACTIVETAB)
-        ? gClipboardHelper.copyString(aWindow.gBrowser.currentURI.spec)
-        : gClipboardHelper.copyString(aUri);
-    } catch (e) {
-      throw new Error(
-        "We're sorry but something has gone wrong with 'CopyTabUrl' " + e
-      );
-    }
-  },
-
-  // Copies all tab urls to clipboard
-  copyAllTabUrls(aWindow) {
-    const gClipboardHelper = Cc[
-      "@mozilla.org/widget/clipboardhelper;1"
-    ].getService(Ci.nsIClipboardHelper);
-    //Get all urls
-    let urlArr = this._getAllUrls(aWindow);
-    try {
-      // Enumerate all urls in to a list.
-      let urlList = urlArr.join("\n");
-      // Send list to clipboard.
-      gClipboardHelper.copyString(urlList.trim());
-      // Clear url list after clipboard event
-      urlList = "";
-    } catch (e) {
-      throw new Error(
-        "We're sorry but something has gone wrong with 'copyAllTabUrls' " + e
-      );
-    }
-  },
-
-  // Get all the tab urls into an array.
-  _getAllUrls(aWindow) {
-    // We don't want to copy about uri's
-    let blocklist = /^about:.*/i;
-    let urlArr = [];
-    let tabCount = aWindow.gBrowser.browsers.length;
-    Array(tabCount)
-      .fill()
-      .map((_, i) => {
-        let spec = aWindow.gBrowser.getBrowserAtIndex(i).currentURI.spec;
-        if (!blocklist.test(spec)) {
-          urlArr.push(spec);
-        }
-      });
-    return urlArr;
-  },
-
-  async restartBrowser() {
-    try {
-      if (Services.prefs.getBoolPref(this.PREF_REQUIRECONFIRM)) {
-        // Need brand in here to be able to expand { -brand-short-name }
-        let l10n = new Localization([
-          "branding/brand.ftl",
-          "browser/waterfox.ftl",
-        ]);
-        let [title, question] = (
-          await l10n.formatMessages([
-            { id: "restart-prompt-title" },
-            { id: "restart-prompt-question" },
-          ])
-        ).map(({ value }) => value);
-
-        if (Services.prompt.confirm(null, title, question)) {
-          // only restart if confirmation given
-          this._attemptRestart();
-        }
-      } else {
-        this._attemptRestart();
-      }
-    } catch (e) {
-      Cu.reportError(
-        "We're sorry but something has gone wrong with 'restartBrowser' " + e
-      );
-    }
-  },
-
-  _attemptRestart() {
-    // Purge cache if required
-    if (Services.prefs.getBoolPref(this.PREF_PURGECACHE)) {
-      Services.appinfo.invalidateCachesOnRestart();
-    }
-
-    // Initiate the restart
-    Services.startup.quit(
-      Services.startup.eRestart | Services.startup.eAttemptQuit
-    );
-  },
-};
diff --git a/waterfox/browser/components/tabfeatures/TabFeatures.sys.mjs b/waterfox/browser/components/tabfeatures/TabFeatures.sys.mjs
new file mode 100644
index 000000000000..6e55cfa84fd1
--- /dev/null
+++ b/waterfox/browser/components/tabfeatures/TabFeatures.sys.mjs
@@ -0,0 +1,322 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AboutNewTab: "resource:///modules/AboutNewTab.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+});
+
+export const TabFeatures = {
+  NEW_TAB_CONFIG_PATH: "browser.newtab.url",
+  newTabURL: null,
+  prefListener: null,
+  PREF_ACTIVETAB: "browser.tabs.copyurl.activetab",
+  PREF_REQUIRECONFIRM: "browser.restart_menu.requireconfirm",
+  PREF_PURGECACHE: "browser.restart_menu.purgecache",
+
+  init(aWindow) {
+    // Wait for XUL elements to be available before initializing listeners.
+    // 'context_copyTabUrl' is an element from our associated XUL, which we will now wait for.
+    if (!aWindow.document.getElementById("context_copyTabUrl")) {
+      lazy.setTimeout(() => {
+        this.init(aWindow);
+      }, 50); // Retry after 50ms
+      return;
+    }
+
+    aWindow.TabFeatures = this;
+    this.initListeners(aWindow);
+    this.initNewTabConfig(); // Does not require aWindow
+    this.initNewTabFocus(aWindow);
+  },
+
+  destroy() {
+    this.destroyNewTabConfig();
+  },
+
+  initListeners(aWindow) {
+    const doc = aWindow.document;
+
+    doc
+      .getElementById("tabContextMenu")
+      ?.addEventListener("popupshowing", this.tabContext.bind(this));
+    if (AppConstants.platform === "macosx") {
+      doc
+        .getElementById("file-menu")
+        ?.addEventListener("popupshowing", this.tabContext.bind(this));
+    } else {
+      doc
+        .getElementById("appMenu-popup")
+        ?.addEventListener("popupshowing", this.tabContext.bind(this));
+    }
+
+    const copyTabUrlElement = doc.getElementById("context_copyTabUrl");
+    if (copyTabUrlElement) {
+      copyTabUrlElement.addEventListener("command", (_event) => {
+        if (aWindow.TabContextMenu?.contextTab?.linkedBrowser) {
+          try {
+            this.copyTabUrl(
+              aWindow.TabContextMenu.contextTab.linkedBrowser.currentURI.spec,
+              aWindow
+            );
+          } catch (e) {
+            console.error(
+              "TabFeatures: Error inside copyTabUrl listener execution:",
+              e
+            );
+          }
+        } else {
+          // console.warn("TabFeatures: copyTabUrl not called, context or linkedBrowser not available.");
+        }
+      });
+    } else {
+      console.error(
+        "TabFeatures: FAILED to find element 'context_copyTabUrl'. Listener NOT attached."
+      );
+    }
+
+    doc
+      .getElementById("context_copyAllTabUrls")
+      ?.addEventListener("command", (_event) => {
+        this.copyAllTabUrls(aWindow);
+      });
+
+    doc
+      .getElementById("context_unloadTab")
+      ?.addEventListener("command", (_event) => {
+        if (
+          aWindow.gBrowser &&
+          aWindow.TabContextMenu &&
+          aWindow.TabContextMenu.contextTab
+        ) {
+          // Prevent unloading if it's the last tab or the only non-pinned tab in the window
+          if (
+            aWindow.gBrowser.tabs.length > 1 &&
+            (Array.from(aWindow.gBrowser.tabs).filter((t) => !t.pinned).length >
+              1 ||
+              !aWindow.TabContextMenu.contextTab.pinned)
+          ) {
+            aWindow.gBrowser.discardBrowser(aWindow.TabContextMenu.contextTab);
+          } else {
+            // console.log("TabFeatures: discardBrowser not called, conditions not met (e.g., last tab).");
+          }
+        } else {
+          // console.warn("TabFeatures: discardBrowser not called, context not available.");
+        }
+      });
+
+    const restartMac = doc.getElementById("app_restartBrowser");
+    if (restartMac) {
+      restartMac.addEventListener("command", (_event) => {
+        this.restartBrowser();
+      });
+    }
+
+    const restartOther = doc.getElementById("appMenu-restart-button");
+    if (restartOther && restartOther.getAttribute("data-tabfeatures-handler-attached") !== "true") {
+      restartOther.addEventListener("command", (_event) => {
+        this.restartBrowser();
+      });
+      restartOther.setAttribute("data-tabfeatures-handler-attached", "true");
+    }
+  },
+
+  initNewTabConfig() {
+    // Fetch pref if it exists
+    this.newTabURL = Services.prefs.getStringPref(this.NEW_TAB_CONFIG_PATH, "");
+
+    // Only proceed if a value is actually set
+    if (this.newTabURL) {
+      try {
+        lazy.AboutNewTab.newTabURL = this.newTabURL;
+        this.prefListener = Services.prefs.addObserver(
+          this.NEW_TAB_CONFIG_PATH,
+          (_subject, _topic, _data) => {
+            const newURL = Services.prefs.getStringPref(
+              this.NEW_TAB_CONFIG_PATH,
+              ""
+            );
+            if (newURL) {
+              lazy.AboutNewTab.newTabURL = newURL;
+            } else {
+              // If the pref is cleared, revert to default behavior
+              lazy.AboutNewTab.resetNewTabURL();
+            }
+          }
+        );
+      } catch (e) {
+        console.error("Error initializing new tab config:", e);
+      }
+    }
+  },
+
+  initNewTabFocus(window) {
+    window.gBrowser.tabContainer.addEventListener("TabOpen", (event) => {
+      const tab = event.target;
+      const browser = window.gBrowser.getBrowserForTab(tab);
+
+      browser.addEventListener(
+        "load",
+        function onLoad() {
+          browser.removeEventListener("load", onLoad);
+          window.setTimeout(() => {
+            browser.contentWindow.focus();
+          }, 0);
+        },
+        { once: true }
+      );
+    });
+  },
+
+  destroyNewTabConfig() {
+    if (this.prefListener) {
+      Services.prefs.removeObserver(
+        this.NEW_TAB_CONFIG_PATH,
+        this.prefListener
+      );
+      this.prefListener = null;
+    }
+  },
+
+  tabContext(aEvent) {
+    let win = aEvent.view;
+    if (!win) {
+      win = Services.wm.getMostRecentWindow("navigator:browser");
+    }
+    const { document } = win;
+    const elements = document.getElementsByClassName("tabFeature");
+    for (let i = 0; i < elements.length; i++) {
+      const el = elements[i];
+      const pref = el.getAttribute("preference");
+      if (pref) {
+        const visible = Services.prefs.getBoolPref(pref);
+        el.hidden = !visible;
+      }
+    }
+    // Can't unload selected tab, so don't show menu item in that case
+    if (win.TabContextMenu.contextTab === win.gBrowser.selectedTab) {
+      const el = document.getElementById("context_unloadTab");
+      el.hidden = true;
+    }
+
+    // Ensure restart button in App Menu (Windows/Linux) has its handler after template instantiation
+    const restartBtn = document.getElementById("appMenu-restart-button");
+    if (restartBtn) {
+      // Toggle iconic styling to match icon prefs so alignment matches Exit when icons are disabled
+      const iconsDisabled = Services.prefs.getBoolPref("userChrome.icon.disabled", false);
+      const iconsInPanel = Services.prefs.getBoolPref("userChrome.icon.panel", false);
+      const shouldIconic = iconsInPanel && !iconsDisabled;
+      restartBtn.classList.toggle("subviewbutton-iconic", shouldIconic);
+
+      if (restartBtn.getAttribute("data-tabfeatures-handler-attached") !== "true") {
+        restartBtn.addEventListener("command", (_event) => {
+          this.restartBrowser();
+        });
+        restartBtn.setAttribute("data-tabfeatures-handler-attached", "true");
+      }
+    }
+  },
+
+  // Copies current tab url to clipboard
+  copyTabUrl(aUri, aWindow) {
+    const gClipboardHelper = Cc[
+      "@mozilla.org/widget/clipboardhelper;1"
+    ].getService(Ci.nsIClipboardHelper);
+    try {
+      Services.prefs.getBoolPref(this.PREF_ACTIVETAB)
+        ? gClipboardHelper.copyString(aWindow.gBrowser.currentURI.spec)
+        : gClipboardHelper.copyString(aUri);
+    } catch (e) {
+      throw new Error(
+        `We're sorry but something has gone wrong with 'CopyTabUrl' ${e}`
+      );
+    }
+  },
+
+  // Copies all tab urls to clipboard
+  copyAllTabUrls(aWindow) {
+    const gClipboardHelper = Cc[
+      "@mozilla.org/widget/clipboardhelper;1"
+    ].getService(Ci.nsIClipboardHelper);
+    //Get all urls
+    const urlArr = this._getAllUrls(aWindow);
+    try {
+      // Enumerate all urls in to a list.
+      let urlList = urlArr.join("\n");
+      // Send list to clipboard.
+      gClipboardHelper.copyString(urlList.trim());
+      // Clear url list after clipboard event
+      urlList = "";
+    } catch (e) {
+      throw new Error(
+        `We're sorry but something has gone wrong with 'copyAllTabUrls' ${e}`
+      );
+    }
+  },
+
+  // Get all the tab urls into an array.
+  _getAllUrls(aWindow) {
+    // We don't want to copy about uri's
+    const blocklist = /^about:.*/i;
+    const urlArr = [];
+    const tabCount = aWindow.gBrowser.browsers.length;
+    Array(tabCount)
+      .fill()
+      .map((_, i) => {
+        const spec = aWindow.gBrowser.getBrowserAtIndex(i).currentURI.spec;
+        if (!blocklist.test(spec)) {
+          urlArr.push(spec);
+        }
+      });
+    return urlArr;
+  },
+
+  async restartBrowser() {
+    try {
+      if (Services.prefs.getBoolPref(this.PREF_REQUIRECONFIRM)) {
+        // Need brand in here to be able to expand { -brand-short-name }
+        const l10n = new Localization([
+          "branding/brand.ftl",
+          "browser/waterfox.ftl",
+        ]);
+        const [title, question] = (
+          await l10n.formatMessages([
+            { id: "restart-prompt-title" },
+            { id: "restart-prompt-question" },
+          ])
+        ).map(({ value }) => value);
+
+        if (Services.prompt.confirm(null, title, question)) {
+          // only restart if confirmation given
+          this._attemptRestart();
+        }
+      } else {
+        this._attemptRestart();
+      }
+    } catch (e) {
+      console.error(
+        "We're sorry but something has gone wrong with 'restartBrowser' ",
+        e
+      );
+    }
+  },
+
+  _attemptRestart() {
+    // Purge cache if required
+    if (Services.prefs.getBoolPref(this.PREF_PURGECACHE)) {
+      Services.appinfo.invalidateCachesOnRestart();
+    }
+
+    // Initiate the restart
+    Services.startup.quit(
+      Services.startup.eRestart | Services.startup.eAttemptQuit
+    );
+  },
+};
diff --git a/waterfox/browser/components/tabfeatures/content/pinnedtab.css b/waterfox/browser/components/tabfeatures/content/pinnedtab.css
index 39f25ccad9a9..80a7d8ca7d9b 100644
--- a/waterfox/browser/components/tabfeatures/content/pinnedtab.css
+++ b/waterfox/browser/components/tabfeatures/content/pinnedtab.css
@@ -4,8 +4,9 @@
     max-width: 225px;
     min-width: var(--tab-min-width);
     width: 0;
-    transition: min-width 100ms ease-out,
-                max-width 100ms ease-out;
+    transition:
+      min-width 100ms ease-out,
+      max-width 100ms ease-out;
   }
 
   .tabbrowser-tab:is([pinned]):not([fadein]) {
diff --git a/waterfox/browser/components/tabfeatures/content/tabfeatures.xhtml b/waterfox/browser/components/tabfeatures/content/tabfeatures.xhtml
index 0a10d0fe3654..a5878d2aeb0e 100644
--- a/waterfox/browser/components/tabfeatures/content/tabfeatures.xhtml
+++ b/waterfox/browser/components/tabfeatures/content/tabfeatures.xhtml
@@ -8,35 +8,32 @@
     xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
     <popupset id="mainPopupSet">
         <menupopup id="tabContextMenu">
-            <menuitem id="context_duplicateTab" data-lazy-l10n-id="duplicate-tab"
-                oncommand="duplicateTabIn(TabContextMenu.contextTab, 'tab');" class="tabFeature"
-                preference="browser.tabs.duplicateTab" />
             <menuitem id="context_copyTabUrl" class="tabFeature"
-                oncommand="TabFeatures.copyTabUrl(TabContextMenu.contextTab.linkedBrowser.currentURI.spec, window);"
-                data-lazy-l10n-id="copy-url" preference="browser.tabs.copyurl" insertafter="context_duplicateTab" />
-            <menuitem id="context_copyAllTabUrls" class="tabFeature" oncommand="TabFeatures.copyAllTabUrls(window);"
+                data-lazy-l10n-id="copy-url" preference="browser.tabs.copyurl" />
+            <menuitem id="context_copyAllTabUrls" class="tabFeature"
                 data-lazy-l10n-id="copy-all-urls" preference="browser.tabs.copyallurls"
                 insertafter="context_copyTabUrl" />
             <menuitem id="context_unloadTab" class="tabFeature"
-                oncommand="gBrowser.discardBrowser(TabContextMenu.contextTab);" data-lazy-l10n-id="unload-tab"
+                data-lazy-l10n-id="unload-tab"
                 preference="browser.tabs.unloadTab" insertafter="context_copyAllTabUrls" />
         </menupopup>
     </popupset>
 #ifdef XP_MACOSX
     <menubar id="main-menubar">
-        <menuitem id="app_restartBrowser" class="tabFeature" oncommand="TabFeatures.restartBrowser();"
+        <menuitem id="app_restartBrowser" class="tabFeature"
             data-l10n-id="appmenuitem-restart-browser" preference="browser.restart_menu.showpanelmenubtn" hidden="true"
             insertafter="goOfflineMenuitem" />
     </menubar>
 #else
-    <html:template id="appMenu-viewCache">
-        <panelview id="appMenu-protonMainView">
-            <vbox id="appMenu-subview-body" class="panel-subview-body">
-                <toolbarbutton id="appMenu-restart-button" class="subviewbutton subviewbutton-iconic tabFeature"
-                    oncommand="TabFeatures.restartBrowser();" data-l10n-id="appmenuitem-restart-browser"
-                    preference="browser.restart_menu.showpanelmenubtn" hidden="true" />
-            </vbox>
-        </panelview>
-    </html:template>
+   <html:template id="appMenu-viewCache">
+       <panelview id="appMenu-mainView">
+           <vbox class="panel-subview-body">
+               <toolbarbutton id="appMenu-restart-button" class="subviewbutton subviewbutton-iconic tabFeature"
+                   data-l10n-id="appmenuitem-restart-browser"
+                   preference="browser.restart_menu.showpanelmenubtn" hidden="true"
+                   insertbefore="appMenu-quit-button2" />
+           </vbox>
+       </panelview>
+   </html:template>
 #endif
 </overlay>
diff --git a/waterfox/browser/components/tabfeatures/moz.build b/waterfox/browser/components/tabfeatures/moz.build
index 7d8bc9e33233..0d421f29e454 100644
--- a/waterfox/browser/components/tabfeatures/moz.build
+++ b/waterfox/browser/components/tabfeatures/moz.build
@@ -5,7 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 EXTRA_JS_MODULES += [
-    "TabFeatures.jsm",
+    "TabFeatures.sys.mjs",
 ]
 
 BROWSER_CHROME_MANIFESTS += ["test/browser/browser.ini"]
diff --git a/waterfox/browser/components/tabfeatures/test/browser/browser_tabfeatures.js b/waterfox/browser/components/tabfeatures/test/browser/browser_tabfeatures.js
index ef524e729fd0..f86ba098bf83 100644
--- a/waterfox/browser/components/tabfeatures/test/browser/browser_tabfeatures.js
+++ b/waterfox/browser/components/tabfeatures/test/browser/browser_tabfeatures.js
@@ -1,9 +1,7 @@
-"use strict";
-
 add_task(async function testCopyTabUrls() {
   // Make sure elements are present
-  let copyTabUrl = document.getElementById("context_copyTabUrl");
-  let copyAllTabUrls = document.getElementById("context_copyAllTabUrls");
+  const copyTabUrl = document.getElementById("context_copyTabUrl");
+  const copyAllTabUrls = document.getElementById("context_copyAllTabUrls");
   ok(copyTabUrl, "Copy tab URL is included");
   ok(copyAllTabUrls, "Copy all tab URLs is included");
   // Make sure that defaults are set correctly
@@ -27,7 +25,7 @@ add_task(async function testCopyTabUrls() {
 
 add_task(async function testHideDuplicateTab() {
   // Setting duplicateTab pref to false should hide element in all windows
-  let duplicateTab = document.getElementById("context_duplicateTab");
+  const duplicateTab = document.getElementById("context_duplicateTab");
   Services.prefs.setBoolPref(DUPLICATE_TAB_PREF, false);
   await openAndCloseTabContextMenu(gBrowser.selectedTab);
   is(duplicateTab.hidden, true, "Duplicate tab hidden");
@@ -40,13 +38,13 @@ add_task(async function testHideDuplicateTab() {
 
 add_task(async function testRestartItem() {
   // Make sure element is present
-  let restartBrowserMenu = document.getElementById("app_restartBrowser");
+  const restartBrowserMenu = document.getElementById("app_restartBrowser");
   // Need to use PanelMultiView to get PanelUI elements
-  let restartBrowserApp = PanelMultiView.getViewNode(
+  const restartBrowserApp = PanelMultiView.getViewNode(
     document,
     "appMenu-restart-button"
   );
-  if (OS == "macosx") {
+  if (OS === "macosx") {
     ok(restartBrowserMenu, "Restart browser menu bar item is included");
     is(restartBrowserApp, null, "Restart browser appMenu item not included");
     await openAndCloseFileMenu();
@@ -65,7 +63,7 @@ add_task(async function testRestartItem() {
   }
   // Make sure element is hidden
   Services.prefs.setBoolPref(RESTART_PREF, false);
-  if (OS == "macosx") {
+  if (OS === "macosx") {
     await openAndCloseFileMenu();
     is(
       restartBrowserMenu.hidden,
@@ -77,22 +75,22 @@ add_task(async function testRestartItem() {
 });
 
 add_task(async function testCopyUrlFunctionality() {
-  let copyTabUrl = document.getElementById("context_copyTabUrl");
-  let copyAllTabUrls = document.getElementById("context_copyAllTabUrls");
+  const copyTabUrl = document.getElementById("context_copyTabUrl");
+  const copyAllTabUrls = document.getElementById("context_copyAllTabUrls");
   const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, URI1);
-  let browser = tab.linkedBrowser;
+  const browser = tab.linkedBrowser;
   // Test copy tab url copies URL
   await openTabContextMenu(tab);
   EventUtils.synthesizeMouseAtCenter(copyTabUrl, {});
-  let tabURI = await pasteFromClipboard(browser);
+  const tabURI = await pasteFromClipboard(browser);
   is(tabURI, URI1);
   // Test copy all tab urls
   Services.prefs.setBoolPref(COPY_ALL_URLS_PREF, true);
   const tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, URI2);
   await openTabContextMenu(tab);
   EventUtils.synthesizeMouseAtCenter(copyAllTabUrls, {});
-  let tabURIs = await pasteFromClipboard(browser);
-  is(tabURIs, URI1 + "\n" + URI2);
+  const tabURIs = await pasteFromClipboard(browser);
+  is(tabURIs, `${URI1}\n${URI2}`);
   // Test copy active tab pref
   Services.prefs.setBoolPref(COPY_ACTIVE_URL_PREF, true);
   await openTabContextMenu(tab);
diff --git a/waterfox/browser/components/tabfeatures/test/browser/head.js b/waterfox/browser/components/tabfeatures/test/browser/head.js
index 1b41a70509bc..6d261b7413b0 100644
--- a/waterfox/browser/components/tabfeatures/test/browser/head.js
+++ b/waterfox/browser/components/tabfeatures/test/browser/head.js
@@ -1,28 +1,22 @@
-"use strict";
+const { synthesizeDrop, synthesizeMouseAtCenter } = EventUtils;
 
-const { AppConstants } = ChromeUtils.import(
-  "resource://gre/modules/AppConstants.jsm"
-);
+const _COPY_URL_PREF = "browser.tabs.copyurl";
+const _COPY_ALL_URLS_PREF = "browser.tabs.copyallurls";
+const _COPY_ACTIVE_URL_PREF = "browser.tabs.copyurl.activetab";
+const _DUPLICATE_TAB_PREF = "browser.tabs.duplicateTab";
+const _RESTART_PREF = "browser.restart_menu.showpanelmenubtn";
 
-var { synthesizeDrop, synthesizeMouseAtCenter } = EventUtils;
+const _URI1 = "https://test1.example.com/";
+const _URI2 = "https://example.com/";
 
-const COPY_URL_PREF = "browser.tabs.copyurl";
-const COPY_ALL_URLS_PREF = "browser.tabs.copyallurls";
-const COPY_ACTIVE_URL_PREF = "browser.tabs.copyurl.activetab";
-const DUPLICATE_TAB_PREF = "browser.tabs.duplicateTab";
-const RESTART_PREF = "browser.restart_menu.showpanelmenubtn";
-
-const URI1 = "https://test1.example.com/";
-const URI2 = "https://example.com/";
-
-let OS = AppConstants.platform;
+const _OS = AppConstants.platform;
 /**
  * Helper for opening the toolbar context menu.
  */
 async function openTabContextMenu(tab) {
   info("Opening tab context menu");
-  let contextMenu = document.getElementById("tabContextMenu");
-  let openTabContextMenuPromise = BrowserTestUtils.waitForPopupEvent(
+  const contextMenu = document.getElementById("tabContextMenu");
+  const openTabContextMenuPromise = BrowserTestUtils.waitForPopupEvent(
     contextMenu,
     "shown"
   );
@@ -32,7 +26,7 @@ async function openTabContextMenu(tab) {
   return contextMenu;
 }
 
-async function openAndCloseTabContextMenu(tab) {
+async function _openAndCloseTabContextMenu(tab) {
   await openTabContextMenu(tab);
   info("Opened tab context menu");
   await EventUtils.synthesizeKey("VK_ESCAPE", {});
@@ -44,8 +38,8 @@ async function openAndCloseTabContextMenu(tab) {
  */
 async function openFileMenu() {
   info("Opening file menu");
-  let fileMenu = document.getElementById("file-menu");
-  let openFileMenuPromise = BrowserTestUtils.waitForPopupEvent(
+  const fileMenu = document.getElementById("file-menu");
+  const openFileMenuPromise = BrowserTestUtils.waitForPopupEvent(
     fileMenu,
     "shown"
   );
@@ -54,7 +48,7 @@ async function openFileMenu() {
   return fileMenu;
 }
 
-async function openAndCloseFileMenu() {
+async function _openAndCloseFileMenu() {
   await openFileMenu();
   await EventUtils.synthesizeKey("VK_ESCAPE", {});
   info("Closed file menu");
@@ -63,8 +57,8 @@ async function openAndCloseFileMenu() {
 /**
  * Helper for opening toolbar context menu.
  */
-async function openToolbarContextMenu(contextMenu, target) {
-  let popupshown = BrowserTestUtils.waitForEvent(contextMenu, "popupshown");
+async function _openToolbarContextMenu(contextMenu, target) {
+  const popupshown = BrowserTestUtils.waitForEvent(contextMenu, "popupshown");
   EventUtils.synthesizeMouseAtCenter(target, { type: "contextmenu" });
   await popupshown;
 }
@@ -73,15 +67,15 @@ async function openToolbarContextMenu(contextMenu, target) {
  * Helper to paste from clipboard
  */
 
-async function pasteFromClipboard(browser) {
+async function _pasteFromClipboard(browser) {
   return SpecialPowers.spawn(browser, [], () => {
-    let { document } = content;
+    const { document } = content;
     document.body.contentEditable = true;
     document.body.focus();
-    let pastePromise = new Promise(resolve => {
+    const pastePromise = new Promise((resolve) => {
       document.addEventListener(
         "paste",
-        e => {
+        (e) => {
           resolve(e.clipboardData.getData("text/plain"));
         },
         { once: true }