--- a/devtools/client/framework/toolbox.js
+++ b/devtools/client/framework/toolbox.js
@@ -1972,16 +1972,20 @@ Toolbox.prototype = {
     // Ensure split console is visible if console was already loaded in background
     let iframe = this.webconsolePanel.querySelector(".toolbox-panel-iframe");
     if (iframe) {
       this.setIframeVisible(iframe, true);
     }
 
     return this.loadTool("webconsole").then(() => {
       this.component.setIsSplitConsoleActive(true);
+      this._telemetry.recordEvent("devtools.main", "activate", "split_console", null, {
+        "host": this._getTelemetryHostString(),
+        "width": Math.ceil(this.win.outerWidth / 50) * 50
+      });
       this.emit("split-console");
       this.focusConsoleInput();
     });
   },
 
   /**
    * Closes the split console.
    *

--- a/devtools/client/responsive.html/manager.js
+++ b/devtools/client/responsive.html/manager.js
@@ -18,29 +18,32 @@ loader.lazyRequireGetter(this, "swapToIn
 loader.lazyRequireGetter(this, "startup", "devtools/client/responsive.html/utils/window", true);
 loader.lazyRequireGetter(this, "message", "devtools/client/responsive.html/utils/message");
 loader.lazyRequireGetter(this, "showNotification", "devtools/client/responsive.html/utils/notification", true);
 loader.lazyRequireGetter(this, "l10n", "devtools/client/responsive.html/utils/l10n");
 loader.lazyRequireGetter(this, "EmulationFront", "devtools/shared/fronts/emulation", true);
 loader.lazyRequireGetter(this, "PriorityLevels", "devtools/client/shared/components/NotificationBox", true);
 loader.lazyRequireGetter(this, "TargetFactory", "devtools/client/framework/target", true);
 loader.lazyRequireGetter(this, "gDevTools", "devtools/client/framework/devtools", true);
+loader.lazyRequireGetter(this, "Telemetry", "devtools/client/shared/telemetry");
 
 const RELOAD_CONDITION_PREF_PREFIX = "devtools.responsive.reloadConditions.";
 const RELOAD_NOTIFICATION_PREF = "devtools.responsive.reloadNotification.enabled";
 
 function debug(msg) {
   // console.log(`RDM manager: ${msg}`);
 }
 
 /**
  * ResponsiveUIManager is the external API for the browser UI, etc. to use when
  * opening and closing the responsive UI.
  */
 const ResponsiveUIManager = exports.ResponsiveUIManager = {
+  _telemetry: new Telemetry(),
+
   activeTabs: new Map(),
 
   /**
    * Toggle the responsive UI for a tab.
    *
    * @param window
    *        The main browser chrome window.
    * @param tab
@@ -89,21 +92,29 @@ const ResponsiveUIManager = exports.Resp
     if (tab.linkedBrowser.hasAttribute("usercontextid")) {
       this.showNoContainerTabsNotification(window, tab, options);
       return promise.reject(new Error("RDM not available for container tabs."));
     }
     if (!this.isActiveForTab(tab)) {
       this.initMenuCheckListenerFor(window);
 
       // Track whether a toolbox was opened before RDM was opened.
-      let hasToolbox = !!gDevTools.getToolbox(TargetFactory.forTab(tab));
+      const toolbox = gDevTools.getToolbox(TargetFactory.forTab(tab));
+      const hostType = toolbox ? toolbox.hostType : "none";
+      const hasToolbox = !!toolbox;
       if (hasToolbox) {
         Services.telemetry.scalarAdd("devtools.responsive.toolbox_opened_first", 1);
       }
 
+      const t = this._telemetry;
+      t.recordEvent("devtools.main", "activate", "responsive_design", null, {
+        "host": hostType,
+        "width": Math.ceil(window.outerWidth / 50) * 50
+      });
+
       // Track opens keyed by the UI entry point used.
       let { trigger } = options;
       if (!trigger) {
         trigger = "unknown";
       }
       Services.telemetry.keyedScalarAdd("devtools.responsive.open_trigger", trigger, 1);
 
       let ui = new ResponsiveUI(window, tab);

--- a/toolkit/components/telemetry/Events.yaml
+++ b/toolkit/components/telemetry/Events.yaml
@@ -212,8 +212,19 @@ devtools.main:
     release_channel_collection: opt-out
     expiry_version: never
     extra_keys:
       host: "Toolbox host (positioning): bottom, side, window or other."
       width: Toolbox width rounded up to the nearest 50px.
       next_panel: The name of the panel closed, webconsole, inspector, jsdebugger, styleeditor, netmonitor, storage or other.
       panel_name: The name of the panel opened, webconsole, inspector, jsdebugger, styleeditor, netmonitor, storage or other
       reason: debuggerStatement, breakpoint, exception, tab_switch, toolbox_show, initial_panel, toggle_settings_off, toggle_settings_on, key_shortcut, select_next_key, select_prev_key, tool_unloaded, inspect_dom, toolbox_closed, unknown etc.
+  activate:
+    objects: ["responsive_design", "split_console"]
+    bug_numbers: [1455273]
+    notification_emails: ["dev-developer-tools@lists.mozilla.org", "hkirschner@mozilla.com"]
+    record_in_processes: ["main"]
+    description: User activates the responsive_design or split_console in the devtools toolbox.
+    release_channel_collection: opt-out
+    expiry_version: never
+    extra_keys:
+      host: "Toolbox host (positioning): bottom, side, window or other."
+      width: Toolbox width rounded up to the nearest 50px.