diff --git a/browser/base/content/browser-menubar.inc b/browser/base/content/browser-menubar.inc
index 3fc098755e..41734711cd 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 a5a4ae8aa6..0c753520f6 100644
--- a/browser/base/content/browser-sets.inc
+++ b/browser/base/content/browser-sets.inc
@@ -103,10 +103,6 @@
      oncommand="Cc['@mozilla.org/browser/browserglue;1'].getService(Ci.nsIBrowserGlue).sanitize(window);"/>
     <command id="Tools:PrivateBrowsing"
       oncommand="OpenBrowserWindow({private: true});" reserved="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();"/>
     <command id="Social:SharePage" oncommand="SocialShare.sharePage();"/>
diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 8fcbff277a..f92577d964 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -1222,9 +1222,6 @@ var gBrowserInit = {
     BrowserOffline.init();
     IndexedDBPromptHelper.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.
@@ -1656,10 +1653,6 @@ if (AppConstants.platform == "macosx") {
 
     // initialize the sync UI
     gSyncUI.init();
-
-    if (AppConstants.E10S_TESTING_ONLY) {
-      gRemoteTabsUI.init();
-    }
   };
 
   gBrowserInit.nonBrowserWindowShutdown = function() {
@@ -7843,16 +7836,6 @@ var TabContextMenu = {
     for (let menuItem of menuItems)
       menuItem.disabled = disabled;
 
-    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 2c74aecdf6..9a4fa0fd52 100644
--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -98,12 +98,6 @@
                 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" hidden="true"/>
       <menu id="context_sendTabToDevice" label="&sendTabToDevice.label;"
             accesskey="&sendTabToDevice.accesskey;" hidden="true">
diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index 3f4c3518ec..a541d534e0 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -3238,20 +3238,6 @@
         </body>
       </method>
 
-      <!-- Opens a given tab to a non-remote window. -->
-      <method name="openNonRemoteWindow">
-        <parameter name="aTab"/>
-        <body>
-          <![CDATA[
-            if (!this.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"/>
@@ -4597,8 +4583,7 @@
               label = this.mStringBundle.getString(stringID);
             }
           } else {
-            label = tab.getAttribute("label") +
-                      (this.AppConstants.E10S_TESTING_ONLY && tab.linkedBrowser && tab.linkedBrowser.isRemoteBrowser ? " - e10s" : "");
+            label = tab.getAttribute("label");
           }
           event.target.setAttribute("label", label);
         ]]></body>
diff --git a/browser/components/customizableui/CustomizableUI.jsm b/browser/components/customizableui/CustomizableUI.jsm
index 86ff2708ba..3e92b42258 100644
--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -207,15 +207,6 @@ var CustomizableUIInternal = {
       panelPlacements.splice(-1, 0, "developer-button");
     }
 
-    if (AppConstants.E10S_TESTING_ONLY) {
-      if (gPalette.has("e10s-button")) {
-        let newWindowIndex = panelPlacements.indexOf("new-window-button");
-        if (newWindowIndex > -1) {
-          panelPlacements.splice(newWindowIndex + 1, 0, "e10s-button");
-        }
-      }
-    }
-
     let showCharacterEncoding = Services.prefs.getComplexValue(
       "browser.menu.showCharacterEncoding",
       Ci.nsIPrefLocalizedString
diff --git a/browser/components/customizableui/CustomizableWidgets.jsm b/browser/components/customizableui/CustomizableWidgets.jsm
index 1e68b01c11..3e83b081cd 100644
--- a/browser/components/customizableui/CustomizableWidgets.jsm
+++ b/browser/components/customizableui/CustomizableWidgets.jsm
@@ -1258,21 +1258,3 @@ 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: function(aDocument) {
-        let node = aDocument.createElementNS(kNSXUL, "toolbarbutton");
-        node.setAttribute("label", CustomizableUI.getLocalizedProperty(this, "label"));
-        node.setAttribute("tooltiptext", CustomizableUI.getLocalizedProperty(this, "tooltiptext"));
-      },
-      onCommand: function(aEvent) {
-        let win = aEvent.view;
-        win.OpenBrowserWindow({remote: false});
-      },
-    });
-  }
-}
diff --git a/browser/components/preferences/in-content/main.js b/browser/components/preferences/in-content/main.js
index 4f20ba8c33..bac771bece 100644
--- a/browser/components/preferences/in-content/main.js
+++ b/browser/components/preferences/in-content/main.js
@@ -11,11 +11,6 @@ Components.utils.import("resource:///modules/TransientPrefs.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "OS",
                                   "resource://gre/modules/osfile.jsm");
 
-if (AppConstants.E10S_TESTING_ONLY) {
-  XPCOMUtils.defineLazyModuleGetter(this, "UpdateUtils",
-                                    "resource://gre/modules/UpdateUtils.jsm");
-}
-
 var gMainPane = {
   /**
    * Initialization of this.
@@ -83,26 +78,6 @@ var gMainPane = {
     setEventListener("chooseFolder", "command",
                      gMainPane.chooseFolder);
 
-    if (AppConstants.E10S_TESTING_ONLY) {
-      setEventListener("e10sAutoStart", "command",
-                       gMainPane.enableE10SChange);
-      let e10sCheckbox = document.getElementById("e10sAutoStart");
-
-      let e10sPref = document.getElementById("browser.tabs.remote.autostart");
-      let e10sTempPref = document.getElementById("e10sTempPref");
-      let e10sForceEnable = document.getElementById("e10sForceEnable");
-
-      let preffedOn = e10sPref.value || e10sTempPref.value || e10sForceEnable.value;
-
-      if (preffedOn) {
-        // The checkbox is checked if e10s is preffed on and enabled.
-        e10sCheckbox.checked = Services.appinfo.browserTabsRemoteAutostart;
-
-        // but if it's force disabled, then the checkbox is disabled.
-        e10sCheckbox.disabled = !Services.appinfo.browserTabsRemoteAutostart;
-      }
-    }
-
     if (AppConstants.MOZ_DEV_EDITION) {
       let uAppData = OS.Constants.Path.userApplicationDataDir;
       let ignoreSeparateProfile = OS.Path.join(uAppData, "ignore-dev-edition-profile");
@@ -123,36 +98,7 @@ var gMainPane = {
 
   enableE10SChange: function ()
   {
-    if (AppConstants.E10S_TESTING_ONLY) {
-      let e10sCheckbox = document.getElementById("e10sAutoStart");
-      let e10sPref = document.getElementById("browser.tabs.remote.autostart");
-      let e10sTempPref = document.getElementById("e10sTempPref");
-
-      let prefsToChange;
-      if (e10sCheckbox.checked) {
-        // Enabling e10s autostart
-        prefsToChange = [e10sPref];
-      } else {
-        // Disabling e10s autostart
-        prefsToChange = [e10sPref];
-        if (e10sTempPref.value) {
-         prefsToChange.push(e10sTempPref);
-        }
-      }
-
-      let buttonIndex = confirmRestartPrompt(e10sCheckbox.checked, 0,
-                                             true, false);
-      if (buttonIndex == CONFIRM_RESTART_PROMPT_RESTART_NOW) {
-        for (let prefToChange of prefsToChange) {
-          prefToChange.value = e10sCheckbox.checked;
-        }
-
-        Services.startup.quit(Ci.nsIAppStartup.eAttemptQuit |  Ci.nsIAppStartup.eRestart);
-      }
-
-      // Revert the checkbox in case we didn't quit
-      e10sCheckbox.checked = e10sPref.value || e10sTempPref.value;
-    }
+    // **STUB**
   },
 
   separateProfileModeChange: function ()
diff --git a/browser/components/preferences/in-content/main.xul b/browser/components/preferences/in-content/main.xul
index 526bbc714f..8eca118772 100644
--- a/browser/components/preferences/in-content/main.xul
+++ b/browser/components/preferences/in-content/main.xul
@@ -9,18 +9,6 @@
 
 <preferences id="mainPreferences" hidden="true" data-category="paneGeneral">
 
-#ifdef E10S_TESTING_ONLY
-    <preference id="browser.tabs.remote.autostart"
-                name="browser.tabs.remote.autostart"
-                type="bool"/>
-    <preference id="e10sTempPref"
-                name="browser.tabs.remote.autostart.2"
-                type="bool"/>
-    <preference id="e10sForceEnable"
-                name="browser.tabs.remote.force-enable"
-                type="bool"/>
-#endif
-
     <!-- Startup -->
     <preference id="browser.startup.page"
                 name="browser.startup.page"
@@ -135,11 +123,6 @@
   </vbox>
 #endif
 
-#ifdef E10S_TESTING_ONLY
-  <checkbox id="e10sAutoStart"
-            label="&e10sEnabled.label;"/>
-#endif
-
 #ifdef HAVE_SHELL_SERVICE
   <vbox id="defaultBrowserBox">
     <hbox align="center">
diff --git a/browser/themes/linux/jar.mn b/browser/themes/linux/jar.mn
index e09029438b..0bf023f353 100644
--- a/browser/themes/linux/jar.mn
+++ b/browser/themes/linux/jar.mn
@@ -129,9 +129,6 @@ browser.jar:
   skin/classic/browser/syncQuota.css
   skin/classic/browser/syncProgress-horizontalbar.png
   skin/classic/browser/syncProgress-horizontalbar@2x.png
-#ifdef E10S_TESTING_ONLY
-  skin/classic/browser/e10s-64@2x.png (../shared/e10s-64@2x.png)
-#endif
 
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 % override chrome://browser/skin/feeds/audioFeedIcon.png              chrome://browser/skin/feeds/feedIcon.png
diff --git a/browser/themes/osx/jar.mn b/browser/themes/osx/jar.mn
index fd9b6127d8..98ba4e6ea8 100644
--- a/browser/themes/osx/jar.mn
+++ b/browser/themes/osx/jar.mn
@@ -209,9 +209,6 @@ browser.jar:
   skin/classic/browser/yosemite/tab-stroke-end-inactive@2x.png         (tabbrowser/tab-stroke-end-yosemite-inactive@2x.png)
   skin/classic/browser/yosemite/tab-stroke-start-inactive.png          (tabbrowser/tab-stroke-start-yosemite-inactive.png)
   skin/classic/browser/yosemite/tab-stroke-start-inactive@2x.png       (tabbrowser/tab-stroke-start-yosemite-inactive@2x.png)
-#ifdef E10S_TESTING_ONLY
-  skin/classic/browser/e10s-64@2x.png (../shared/e10s-64@2x.png)
-#endif
 
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 % override chrome://browser/skin/feeds/audioFeedIcon.png                   chrome://browser/skin/feeds/feedIcon.png
diff --git a/browser/themes/windows/jar.mn b/browser/themes/windows/jar.mn
index 89c589abad..d39a46b2e0 100644
--- a/browser/themes/windows/jar.mn
+++ b/browser/themes/windows/jar.mn
@@ -193,9 +193,6 @@ browser.jar:
   skin/classic/browser/syncProgress-toolbar-inverted@2x.png
   skin/classic/browser/syncProgress-toolbar-XPVista7.png
   skin/classic/browser/syncProgress-toolbar-XPVista7@2x.png
-#ifdef E10S_TESTING_ONLY
-  skin/classic/browser/e10s-64@2x.png (../shared/e10s-64@2x.png)
-#endif
 
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 % override chrome://browser/skin/page-livemarks.png                   chrome://browser/skin/feeds/feedIcon16.png
diff --git a/devtools/client/performance/performance-controller.js b/devtools/client/performance/performance-controller.js
index e47a0c4010..4bd272f41a 100644
--- a/devtools/client/performance/performance-controller.js
+++ b/devtools/client/performance/performance-controller.js
@@ -527,11 +527,10 @@ var PerformanceController = {
     if (flags.testing) {
       return { supported: true, enabled: true };
     }
-    let supported = system.constants.E10S_TESTING_ONLY;
     // This is only checked on tool startup -- requires a restart if
     // e10s subsequently enabled.
     let enabled = this._e10s;
-    return { supported, enabled };
+    return { supported: false, enabled };
   },
 
   /**
diff --git a/devtools/client/performance/test/browser_perf-recording-notices-05.js b/devtools/client/performance/test/browser_perf-recording-notices-05.js
index b6267470d1..7a6b6b6b92 100644
--- a/devtools/client/performance/test/browser_perf-recording-notices-05.js
+++ b/devtools/client/performance/test/browser_perf-recording-notices-05.js
@@ -41,8 +41,8 @@ add_task(function* () {
   enabled = true;
   PerformanceController._setMultiprocessAttributes();
   ok($("#performance-view").getAttribute("e10s"), "",
-    "When e10s is enabled, but not supported, this probably means we no longer have " +
-    "E10S_TESTING_ONLY, and we have no e10s attribute.");
+    "When e10s is enabled, but not supported, this probably means we " +
+    "have no e10s attribute.");
 
   supported = true;
   enabled = true;
diff --git a/moz.configure b/moz.configure
index 976cbd014e..cecc1335e6 100644
--- a/moz.configure
+++ b/moz.configure
@@ -14,17 +14,6 @@ include('build/moz.configure/init.configure')
 # - Spidermonkey-specific options and rules should go in js/moz.configure.
 # - etc.
 
-# Multiprocess Firefox Testing UI - Nightly and Aurora
-# To be removed in Bug 1003313
-@depends(milestone)
-def e10s_testing_only(milestone):
-    if not milestone.is_release_or_beta:
-        return True
-
-set_config('E10S_TESTING_ONLY', e10s_testing_only)
-set_define('E10S_TESTING_ONLY', e10s_testing_only)
-
-
 option('--enable-artifact-builds', env='MOZ_ARTIFACT_BUILDS',
        help='Download and use prebuilt binary artifacts.')
 
diff --git a/toolkit/modules/AppConstants.jsm b/toolkit/modules/AppConstants.jsm
index 8d9fa103c3..ba5d82c015 100644
--- a/toolkit/modules/AppConstants.jsm
+++ b/toolkit/modules/AppConstants.jsm
@@ -204,13 +204,6 @@ this.AppConstants = Object.freeze({
   false,
 #endif
 
-  E10S_TESTING_ONLY:
-#ifdef E10S_TESTING_ONLY
-  true,
-#else
-  false,
-#endif
-
   DEBUG:
 #ifdef DEBUG
   true,