diff --git a/browser/base/content/browser-menubar.inc b/browser/base/content/browser-menubar.inc
index 6dc75f7547fe..e818cdfafcbe 100644
--- a/browser/base/content/browser-menubar.inc
+++ b/browser/base/content/browser-menubar.inc
@@ -34,12 +34,6 @@
                           accesskey="&newPrivateWindow.accesskey;"
                           command="Tools:PrivateBrowsing"
                           key="key_privatebrowsing"/>
-#ifdef E10S_TESTING_ONLY
-                <menuitem id="menu_newNonRemoteWindow"
-                          label="&newNonRemoteWindow.label;"
-                          hidden="true"
-                          command="Tools:NonRemoteWindow"/>
-#endif
 #ifdef MAC_NON_BROWSER_WINDOW
                 <menuitem id="menu_openLocation"
                           label="&openLocationCmd.label;"
diff --git a/browser/base/content/browser-sets.inc b/browser/base/content/browser-sets.inc
index 49be3820199c..b353313cd07b 100644
--- a/browser/base/content/browser-sets.inc
+++ b/browser/base/content/browser-sets.inc
@@ -102,10 +102,6 @@
      oncommand="Cc['@mozilla.org/browser/browserglue;1'].getService(Ci.nsIBrowserGlue).sanitize(window);"/>
     <command id="Tools:PrivateBrowsing"
       oncommand="OpenBrowserWindow({private: true});"/>
-#ifdef E10S_TESTING_ONLY
-    <command id="Tools:NonRemoteWindow"
-      oncommand="OpenBrowserWindow({remote: false});"/>
-#endif
     <command id="History:UndoCloseTab" oncommand="undoCloseTab();"/>
     <command id="History:UndoCloseWindow" oncommand="undoCloseWindow();"/>
   </commandset>
diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 8831891dc375..12a03b01616c 100755
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -1466,9 +1466,6 @@ var gBrowserInit = {
     IndexedDBPromptHelper.init();
     CanvasPermissionPromptHelper.init();
 
-    if (AppConstants.E10S_TESTING_ONLY)
-      gRemoteTabsUI.init();
-
     // Initialize the full zoom setting.
     // We do this before the session restore service gets initialized so we can
     // apply full zoom settings to tabs restored by the session restore service.
@@ -1982,9 +1979,6 @@ if (AppConstants.platform == "macosx") {
     // initialize the private browsing UI
     gPrivateBrowsingUI.init();
 
-    if (AppConstants.E10S_TESTING_ONLY) {
-      gRemoteTabsUI.init();
-    }
   };
 
   gBrowserInit.nonBrowserWindowShutdown = function() {
@@ -8283,27 +8277,6 @@ var gPrivateBrowsingUI = {
   }
 };
 
-var gRemoteTabsUI = {
-  init() {
-    if (window.location.href != getBrowserURL() &&
-        // Also check hidden window for the Mac no-window case
-        window.location.href != "chrome://browser/content/hiddenWindow.xul") {
-      return;
-    }
-
-    if (AppConstants.platform == "macosx" &&
-        Services.prefs.getBoolPref("layers.acceleration.disabled")) {
-      // On OS X, "Disable Hardware Acceleration" also disables OMTC and forces
-      // a fallback to Basic Layers. This is incompatible with e10s.
-      return;
-    }
-
-    let newNonRemoteWindow = document.getElementById("menu_newNonRemoteWindow");
-    let autostart = Services.appinfo.browserTabsRemoteAutostart;
-    newNonRemoteWindow.hidden = !autostart;
-  }
-};
-
 /**
  * Switch to a tab that has a given URI, and focuses its browser window.
  * If a matching tab is in this window, it will be switched to. Otherwise, other
@@ -8561,16 +8534,6 @@ var TabContextMenu = {
     if (this.contextTab.hasAttribute("customizemode"))
       document.getElementById("context_openTabInWindow").disabled = true;
 
-    if (AppConstants.E10S_TESTING_ONLY) {
-      menuItems = aPopupMenu.getElementsByAttribute("tbattr", "tabbrowser-remote");
-      for (let menuItem of menuItems) {
-        menuItem.hidden = !gMultiProcessBrowser;
-        if (menuItem.id == "context_openNonRemoteWindow") {
-          menuItem.disabled = !!parseInt(this.contextTab.getAttribute("usercontextid"));
-        }
-      }
-    }
-
     disabled = gBrowser.visibleTabs.length == 1;
     menuItems = aPopupMenu.getElementsByAttribute("tbattr", "tabbrowser-multiple-visible");
     for (let menuItem of menuItems)
diff --git a/browser/base/content/browser.xul b/browser/base/content/browser.xul
index 206575daa5c6..3058058ab390 100644
--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -96,12 +96,6 @@
                 accesskey="&moveToNewWindow.accesskey;"
                 tbattr="tabbrowser-multiple"
                 oncommand="gBrowser.replaceTabWithWindow(TabContextMenu.contextTab);"/>
-#ifdef E10S_TESTING_ONLY
-      <menuitem id="context_openNonRemoteWindow" label="Open in new non-e10s window"
-                tbattr="tabbrowser-remote"
-                hidden="true"
-                oncommand="gBrowser.openNonRemoteWindow(TabContextMenu.contextTab);"/>
-#endif
       <menuseparator id="context_sendTabToDevice_separator"/>
       <menu id="context_sendTabToDevice" label="&sendTabToDevice.label;"
             accesskey="&sendTabToDevice.accesskey;">
diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index df1e479d677b..e14f5955d253 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -3954,20 +3954,6 @@
         </body>
       </method>
 
-      <!-- Opens a given tab to a non-remote window. -->
-      <method name="openNonRemoteWindow">
-        <parameter name="aTab"/>
-        <body>
-          <![CDATA[
-            if (!AppConstants.E10S_TESTING_ONLY) {
-              throw "This method is intended only for e10s testing!";
-            }
-            let url = aTab.linkedBrowser.currentURI.spec;
-            return window.openDialog("chrome://browser/content/", "_blank", "chrome,all,dialog=no,non-remote", url);
-          ]]>
-        </body>
-      </method>
-
       <method name="moveTabTo">
         <parameter name="aTab"/>
         <parameter name="aIndex"/>
@@ -5544,14 +5530,11 @@
             }
           } else {
             label = tab._fullLabel || tab.getAttribute("label");
-            if (AppConstants.E10S_TESTING_ONLY &&
+            if (AppConstants.NIGHTLY_BUILD &&
                 tab.linkedBrowser &&
-                tab.linkedBrowser.isRemoteBrowser) {
-              label += " - e10s";
-              if (tab.linkedBrowser.frameLoader &&
-                  Services.appinfo.maxWebProcessCount > 1) {
-                label += " (" + tab.linkedBrowser.frameLoader.tabParent.osPid + ")";
-              }
+                tab.linkedBrowser.isRemoteBrowser &&
+                tab.linkedBrowser.frameLoader) {
+              label += " (pid " + tab.linkedBrowser.frameLoader.tabParent.osPid + ")";
             }
             if (tab.userContextId) {
               label = this.mStringBundle.getFormattedString("tabs.containers.tooltip", [label, ContextualIdentityService.getUserContextLabel(tab.userContextId)]);
diff --git a/browser/components/customizableui/CustomizableUI.jsm b/browser/components/customizableui/CustomizableUI.jsm
index de20ffe7e87c..81dd963122b9 100644
--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -59,7 +59,7 @@ const kSubviewEvents = [
  * The current version. We can use this to auto-add new default widgets as necessary.
  * (would be const but isn't because of testing purposes)
  */
-var kVersion = 12;
+var kVersion = 13;
 
 /**
  * Buttons removed from built-ins by version they were removed. kVersion must be
@@ -345,7 +345,6 @@ var CustomizableUIInternal = {
         "preferences-button",
         "add-ons-button",
         "sync-button",
-        "e10s-button",
       ];
 
       if (!AppConstants.MOZ_DEV_EDITION) {
@@ -452,6 +451,17 @@ var CustomizableUIInternal = {
         }
       }
     }
+
+    // Remove the old placements from the now-gone Nightly-only
+    // "New non-e10s window" button.
+    if (currentVersion < 13 && gSavedState.placements) {
+      for (let placements of Object.values(gSavedState.placements)) {
+        let buttonIndex = placements.indexOf("e10s-button");
+        if (buttonIndex != -1) {
+          placements.spice(buttonIndex, 1);
+        }
+      }
+    }
   },
 
   /**
diff --git a/browser/components/customizableui/CustomizableWidgets.jsm b/browser/components/customizableui/CustomizableWidgets.jsm
index 4ce4f7baf077..936cf374b3aa 100644
--- a/browser/components/customizableui/CustomizableWidgets.jsm
+++ b/browser/components/customizableui/CustomizableWidgets.jsm
@@ -997,21 +997,3 @@ if (Services.prefs.getBoolPref("privacy.panicButton.enabled")) {
     },
   });
 }
-
-if (AppConstants.E10S_TESTING_ONLY) {
-  if (Services.appinfo.browserTabsRemoteAutostart) {
-    CustomizableWidgets.push({
-      id: "e10s-button",
-      defaultArea: CustomizableUI.AREA_PANEL,
-      onBuild(aDocument) {
-        let node = aDocument.createElementNS(kNSXUL, "toolbarbutton");
-        node.setAttribute("label", CustomizableUI.getLocalizedProperty(this, "label"));
-        node.setAttribute("tooltiptext", CustomizableUI.getLocalizedProperty(this, "tooltiptext"));
-      },
-      onCommand(aEvent) {
-        let win = aEvent.view;
-        win.OpenBrowserWindow({remote: false});
-      },
-    });
-  }
-}
diff --git a/browser/components/customizableui/test/head.js b/browser/components/customizableui/test/head.js
index 5267dcf2da21..c4faea4e02c0 100644
--- a/browser/components/customizableui/test/head.js
+++ b/browser/components/customizableui/test/head.js
@@ -17,11 +17,6 @@ Services.scriptloader.loadSubScript("chrome://mochikit/content/tests/SimpleTest/
 Services.prefs.setBoolPref("browser.uiCustomization.skipSourceNodeCheck", true);
 registerCleanupFunction(() => Services.prefs.clearUserPref("browser.uiCustomization.skipSourceNodeCheck"));
 
-// Remove temporary e10s related new window options in customize ui,
-// they break a lot of tests.
-CustomizableUI.destroyWidget("e10s-button");
-CustomizableUI.removeWidgetFromArea("e10s-button");
-
 var {synthesizeDragStart, synthesizeDrop} = EventUtils;
 
 const kNSXUL = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
diff --git a/browser/locales/en-US/chrome/browser/browser.dtd b/browser/locales/en-US/chrome/browser/browser.dtd
index dfbaeaba44cd..1103f042a06d 100644
--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -294,7 +294,6 @@ These should match what Safari and other Apple applications use on OS X Lion. --
 <!ENTITY newNavigatorCmd.accesskey      "N">
 <!ENTITY newPrivateWindow.label     "New Private Window">
 <!ENTITY newPrivateWindow.accesskey "W">
-<!ENTITY newNonRemoteWindow.label   "New Non-e10s Window">
 
 <!ENTITY editMenu.label         "Edit">
 <!ENTITY editMenu.accesskey       "E">
diff --git a/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties b/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
index 84403c3ef53a..762068a1688b 100644
--- a/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
+++ b/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
@@ -101,9 +101,6 @@ panic-button.tooltiptext = Forget about some browsing history
 devtools-webide-button2.label = WebIDE
 devtools-webide-button2.tooltiptext = Open WebIDE (%S)
 
-e10s-button.label = New Non-e10s Window
-e10s-button.tooltiptext = Open a new Non-e10s Window
-
 toolbarspring.label = Flexible Space
 toolbarseparator.label = Separator
 toolbarspacer.label = Space
diff --git a/browser/themes/shared/toolbarbutton-icons.inc.css b/browser/themes/shared/toolbarbutton-icons.inc.css
index 9ee2107c3397..d1e672db7f46 100644
--- a/browser/themes/shared/toolbarbutton-icons.inc.css
+++ b/browser/themes/shared/toolbarbutton-icons.inc.css
@@ -229,14 +229,6 @@ toolbar[brighttext] {
   list-style-image: url("chrome://browser/skin/new-window.svg");
 }
 
-#e10s-button {
-  list-style-image: url("chrome://browser/skin/new-window.svg");
-}
-
-#e10s-button > .toolbarbutton-icon {
-  transform: scaleY(-1);
-}
-
 #new-tab-button {
   list-style-image: url("chrome://browser/skin/new-tab.svg");
 }