--- a/devtools/client/devtools-startup.js
+++ b/devtools/client/devtools-startup.js
@@ -245,17 +245,17 @@ DevToolsStartup.prototype = {
       viewId: "PanelUI-developer",
       shortcutId: "key_toggleToolbox",
       tooltiptext: "developer-button.tooltiptext2",
       defaultArea: AppConstants.MOZ_DEV_EDITION ?
                      CustomizableUI.AREA_NAVBAR :
                      CustomizableUI.AREA_PANEL,
       onViewShowing: (event) => {
         // Ensure creating the menuitems in the system menu before trying to copy them.
-        this.initDevTools();
+        this.initDevTools("HamburgerMenu");
 
         // Populate the subview with whatever menuitems are in the developer
         // menu. We skip menu elements, because the menu panel has no way
         // of dealing with those right now.
         let doc = event.target.ownerDocument;
 
         let menu = doc.getElementById("menuWebDeveloperPopup");
 
@@ -295,17 +295,19 @@ DevToolsStartup.prototype = {
 
   /*
    * We listen to the "Web Developer" system menu, which is under "Tools" main item.
    * This menu item is hardcoded empty in Firefox UI. We listen for its opening to
    * populate it lazily. Loading main DevTools module is going to populate it.
    */
   hookWebDeveloperMenu(window) {
     let menu = window.document.getElementById("webDeveloperMenu");
-    menu.addEventListener("popupshowing", () => this.initDevTools(), { once: true });
+    menu.addEventListener("popupshowing", () => {
+      this.initDevTools("SystemMenu");
+    }, { once: true });
   },
 
   hookKeyShortcuts(window) {
     let doc = window.document;
     let keyset = doc.createElement("keyset");
     keyset.setAttribute("id", "devtoolsKeyset");
 
     for (let key of KeyShortcuts) {
@@ -316,17 +318,17 @@ DevToolsStartup.prototype = {
     // Appending a <key> element is not always enough. The <keyset> needs
     // to be detached and reattached to make sure the <key> is taken into
     // account (see bug 832984).
     let mainKeyset = doc.getElementById("mainKeyset");
     mainKeyset.parentNode.insertBefore(keyset, mainKeyset);
   },
 
   onKey(window, key) {
-    let require = this.initDevTools();
+    let require = this.initDevTools("KeyShortcut");
     let { gDevToolsBrowser } = require("devtools/client/framework/devtools-browser");
     gDevToolsBrowser.onKeyShortcut(window, key);
   },
 
   // Create a <xul:key> DOM Element
   createKey(doc, { id, toolId, shortcut, modifiers: mod }, oncommand) {
     let k = doc.createElement("key");
     k.id = "key_" + (id || toolId);
@@ -349,29 +351,40 @@ DevToolsStartup.prototype = {
   },
 
   /**
    * Boolean flag to check if DevTools have been already initialized or not.
    * By initialized, we mean that its main modules are loaded.
    */
   initialized: false,
 
-  initDevTools: function () {
+  initDevTools: function (reason) {
+    if (!this.initialized) {
+      // Only save the first call for each firefox run as next call
+      // won't necessarely start the tool. For example key shortcuts may
+      // only change the currently selected tool.
+      try {
+        Services.telemetry.getHistogramById("DEVTOOLS_ENTRY_POINT")
+                          .add(reason);
+      } catch (e) {
+        dump("DevTools telemetry entry point failed: " + e + "\n");
+      }
+    }
     this.initialized = true;
     let { require } = Cu.import("resource://devtools/shared/Loader.jsm", {});
     // Ensure loading main devtools module that hooks up into browser UI
     // and initialize all devtools machinery.
     require("devtools/client/framework/devtools-browser");
     return require;
   },
 
   handleConsoleFlag: function (cmdLine) {
     let window = Services.wm.getMostRecentWindow("devtools:webconsole");
     if (!window) {
-      this.initDevTools();
+      this.initDevTools("CommandLine");
 
       let { require } = Cu.import("resource://devtools/shared/Loader.jsm", {});
       let hudservice = require("devtools/client/webconsole/hudservice");
       let { console } = Cu.import("resource://gre/modules/Console.jsm", {});
       hudservice.toggleBrowserConsole().catch(console.error);
     } else {
       // the Browser Console was already open
       window.focus();
@@ -379,17 +392,17 @@ DevToolsStartup.prototype = {
 
     if (cmdLine.state == Ci.nsICommandLine.STATE_REMOTE_AUTO) {
       cmdLine.preventDefault = true;
     }
   },
 
   // Open the toolbox on the selected tab once the browser starts up.
   handleDevToolsFlag: function (window) {
-    const require = this.initDevTools();
+    const require = this.initDevTools("CommandLine");
     const {gDevTools} = require("devtools/client/framework/devtools");
     const {TargetFactory} = require("devtools/client/framework/target");
     let target = TargetFactory.forTab(window.gBrowser.selectedTab);
     gDevTools.showToolbox(target);
   },
 
   _isRemoteDebuggingEnabled() {
     let remoteDebuggingEnabled = false;

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -9321,16 +9321,26 @@
   "WEBRTC_CALL_TYPE": {
     "record_in_processes": ["main", "content"],
     "alert_emails": ["webrtc-telemetry-alerts@mozilla.com"],
     "expires_in_version": "never",
     "kind": "enumerated",
     "n_values": 8,
     "description": "Type of call: (Bitmask) Audio = 1, Video = 2, DataChannels = 4"
   },
+  "DEVTOOLS_ENTRY_POINT": {
+    "record_in_processes": ["main"],
+    "bug_numbers": [1378863],
+    "alert_emails": ["dev-developer-tools@lists.mozilla.org", "apoirot@mozilla.com"],
+    "expires_in_version": "60",
+    "kind": "categorical",
+    "labels": ["KeyShortcut", "SystemMenu", "HamburgerMenu", "ContextMenu", "CommandLine"],
+    "releaseChannelCollection": "opt-out",
+    "description": "Records how the user is triggering Developer Tools startup."
+  },
   "DEVTOOLS_TOOLBOX_OPENED_COUNT": {
     "record_in_processes": ["main", "content"],
     "alert_emails": ["dev-developer-tools@lists.mozilla.org"],
     "expires_in_version": "never",
     "kind": "count",
     "bug_numbers": [1247985],
     "description": "Number of times the DevTools toolbox has been opened.",
     "releaseChannelCollection": "opt-out"