--- a/browser/components/customizableui/CustomizableWidgets.jsm
+++ b/browser/components/customizableui/CustomizableWidgets.jsm
@@ -16,17 +16,16 @@ XPCOMUtils.defineLazyModuleGetters(this,
   BrowserUITelemetry: "resource:///modules/BrowserUITelemetry.jsm",
   PlacesUtils: "resource://gre/modules/PlacesUtils.jsm",
   PlacesUIUtils: "resource:///modules/PlacesUIUtils.jsm",
   RecentlyClosedTabsAndWindowsMenuUtils: "resource:///modules/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm",
   ShortcutUtils: "resource://gre/modules/ShortcutUtils.jsm",
   CharsetMenu: "resource://gre/modules/CharsetMenu.jsm",
   PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.jsm",
   SyncedTabs: "resource://services-sync/SyncedTabs.jsm",
-  ContextualIdentityService: "resource://gre/modules/ContextualIdentityService.jsm",
 });
 
 XPCOMUtils.defineLazyGetter(this, "CharsetBundle", function() {
   const kCharsetBundle = "chrome://global/locale/charsetMenu.properties";
   return Services.strings.createBundle(kCharsetBundle);
 });
 XPCOMUtils.defineLazyGetter(this, "BrandBundle", function() {
   const kBrandBundle = "chrome://branding/locale/brand.properties";
@@ -909,99 +908,16 @@ const CustomizableWidgets = [
     }
   }, {
     id: "email-link-button",
     tooltiptext: "email-link-button.tooltiptext3",
     onCommand(aEvent) {
       let win = aEvent.view;
       win.MailIntegration.sendLinkForBrowser(win.gBrowser.selectedBrowser)
     }
-  }, {
-    id: "containers-panelmenu",
-    type: "view",
-    viewId: "PanelUI-containers",
-    hasObserver: false,
-    onCreated(aNode) {
-      let doc = aNode.ownerDocument;
-      let win = doc.defaultView;
-      let items = doc.getElementById("PanelUI-containersItems");
-
-      let onItemCommand = function(aEvent) {
-        let item = aEvent.target;
-        if (item.hasAttribute("usercontextid")) {
-          let userContextId = parseInt(item.getAttribute("usercontextid"));
-          win.openUILinkIn(win.BROWSER_NEW_TAB_URL, "tab", {userContextId});
-        }
-      };
-      items.addEventListener("command", onItemCommand);
-
-      if (PrivateBrowsingUtils.isWindowPrivate(win)) {
-        aNode.setAttribute("disabled", "true");
-      }
-
-      this.updateVisibility(aNode);
-
-      if (!this.hasObserver) {
-        Services.prefs.addObserver("privacy.userContext.enabled", this, true);
-        this.hasObserver = true;
-      }
-    },
-    onViewShowing(aEvent) {
-      let doc = aEvent.target.ownerDocument;
-
-      let items = doc.getElementById("PanelUI-containersItems");
-
-      while (items.firstChild) {
-        items.firstChild.remove();
-      }
-
-      let fragment = doc.createDocumentFragment();
-      let bundle = doc.getElementById("bundle_browser");
-
-      ContextualIdentityService.getPublicIdentities().forEach(identity => {
-        let label = ContextualIdentityService.getUserContextLabel(identity.userContextId);
-
-        let item = doc.createElementNS(kNSXUL, "toolbarbutton");
-        item.setAttribute("label", label);
-        item.setAttribute("usercontextid", identity.userContextId);
-        item.setAttribute("class", "subviewbutton");
-        item.setAttribute("data-identity-color", identity.color);
-        item.setAttribute("data-identity-icon", identity.icon);
-
-        fragment.appendChild(item);
-      });
-
-      fragment.appendChild(doc.createElementNS(kNSXUL, "menuseparator"));
-
-      let item = doc.createElementNS(kNSXUL, "toolbarbutton");
-      item.setAttribute("label", bundle.getString("userContext.aboutPage.label"));
-      item.setAttribute("command", "Browser:OpenAboutContainers");
-      item.setAttribute("class", "subviewbutton");
-      fragment.appendChild(item);
-
-      items.appendChild(fragment);
-    },
-
-    updateVisibility(aNode) {
-      aNode.hidden = !Services.prefs.getBoolPref("privacy.userContext.enabled");
-    },
-
-    observe(aSubject, aTopic, aData) {
-      let {instances} = CustomizableUI.getWidget("containers-panelmenu");
-      for (let {node} of instances) {
-        if (node) {
-          this.updateVisibility(node);
-        }
-      }
-    },
-
-    QueryInterface: XPCOMUtils.generateQI([
-      Ci.nsISupportsWeakReference,
-      Ci.nsIObserver
-    ]),
   }];
 
 let preferencesButton = {
   id: "preferences-button",
   defaultArea: CustomizableUI.AREA_PANEL,
   onCommand(aEvent) {
     let win = aEvent.target.ownerGlobal;
     win.openPreferences(undefined, {origin: "preferencesButton"});

--- a/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
+++ b/browser/locales/en-US/chrome/browser/customizableui/customizableWidgets.properties
@@ -71,19 +71,16 @@ copy-button.tooltiptext2 = Copy (%S)
 
 paste-button.label = Paste
 # LOCALIZATION NOTE(paste-button.tooltiptext2): %S is the keyboard shortcut.
 paste-button.tooltiptext2 = Paste (%S)
 
 feed-button.label = Subscribe
 feed-button.tooltiptext2 = Subscribe to this page
 
-containers-panelmenu.label = Open Container Tab
-containers-panelmenu.tooltiptext = Open Container Tab
-
 # LOCALIZATION NOTE (characterencoding-button2.label): The \u00ad text at the beginning
 # of the string is used to disable auto hyphenation on the button text when it is displayed
 # in the menu panel.
 characterencoding-button2.label = \u00adText Encoding
 characterencoding-button2.tooltiptext = Show text encoding options
 
 email-link-button.label = Email Link
 email-link-button.tooltiptext3 = Email a link to this page

--- a/browser/modules/BrowserUITelemetry.jsm
+++ b/browser/modules/BrowserUITelemetry.jsm
@@ -87,17 +87,16 @@ XPCOMUtils.defineLazyGetter(this, "DEFAU
 XPCOMUtils.defineLazyGetter(this, "PALETTE_ITEMS", function() {
   let result = [
     "bookmarks-menu-button",
     "search-container",
     "open-file-button",
     "developer-button",
     "feed-button",
     "email-link-button",
-    "containers-panelmenu",
     ...LEGACY_PANEL_PLACEMENTS,
     "characterencoding-button",
   ];
 
   if (Services.prefs.getBoolPref("privacy.panicButton.enabled")) {
     result.push("panic-button");
   }
 

deleted file mode 100644
--- a/browser/themes/shared/icons/containers.svg
+++ /dev/null
@@ -1,6 +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/. -->
-<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
-  <path fill="context-fill" fill-opacity="context-fill-opacity" d="M12 4H4v4h8zm-2 2.75a.25.25 0 0 1-.25.25h-3.5A.25.25 0 0 1 6 6.75v-.5A.25.25 0 0 1 6.25 6h3.5a.25.25 0 0 1 .25.25zM12 9H4v4h8zm-2 2.75a.25.25 0 0 1-.25.25h-3.5a.25.25 0 0 1-.25-.25v-.5a.25.25 0 0 1 .25-.25h3.5a.25.25 0 0 1 .25.25zm3.854-9.9L13 1H3l-.854.853A.5.5 0 0 0 2 2.207V14a1 1 0 0 0 1 1h10a1 1 0 0 0 1-1V2.207a.5.5 0 0 0-.146-.354zM13 14H3V3h10z"/>
-</svg>

--- a/browser/themes/shared/jar.inc.mn
+++ b/browser/themes/shared/jar.inc.mn
@@ -123,17 +123,16 @@
   skin/classic/browser/bookmark-animation.svg         (../shared/icons/bookmark-animation.svg)
   skin/classic/browser/bookmark-hollow.svg            (../shared/icons/bookmark-hollow.svg)
   skin/classic/browser/bookmark-star-on-tray.svg      (../shared/icons/bookmark-star-on-tray.svg)
   skin/classic/browser/characterEncoding.svg          (../shared/icons/characterEncoding.svg)
   skin/classic/browser/chevron.svg                    (../shared/icons/chevron.svg)
   skin/classic/browser/chevron-animation.svg          (../shared/icons/chevron-animation.svg)
   skin/classic/browser/check.svg                      (../shared/icons/check.svg)
   skin/classic/browser/check-animation.svg            (../shared/icons/check-animation.svg)
-  skin/classic/browser/containers.svg                 (../shared/icons/containers.svg)
   skin/classic/browser/customize.svg                  (../shared/icons/customize.svg)
   skin/classic/browser/developer.svg                  (../shared/icons/developer.svg)
   skin/classic/browser/device-mobile.svg              (../shared/icons/device-mobile.svg)
   skin/classic/browser/device-tablet.svg              (../shared/icons/device-tablet.svg)
   skin/classic/browser/device-desktop.svg             (../shared/icons/device-desktop.svg)
   skin/classic/browser/edit-copy.svg                  (../shared/icons/edit-copy.svg)
   skin/classic/browser/edit-cut.svg                   (../shared/icons/edit-cut.svg)
   skin/classic/browser/edit-paste.svg                 (../shared/icons/edit-paste.svg)

--- a/browser/themes/shared/toolbarbutton-icons.inc.css
+++ b/browser/themes/shared/toolbarbutton-icons.inc.css
@@ -211,20 +211,16 @@ toolbar[brighttext] {
 #save-page-button {
   list-style-image: url("chrome://browser/skin/save.svg");
 }
 
 #sync-button {
   list-style-image: url("chrome://browser/skin/synced-tabs.svg");
 }
 
-#containers-panelmenu {
-  list-style-image: url("chrome://browser/skin/containers.svg");
-}
-
 #feed-button {
   list-style-image: url("chrome://browser/skin/feed.svg");
 }
 
 #characterencoding-button {
   list-style-image: url("chrome://browser/skin/characterEncoding.svg");
 }