--- a/browser/components/nsBrowserContentHandler.js
+++ b/browser/components/nsBrowserContentHandler.js
@@ -689,28 +689,16 @@ nsDefaultCommandLineHandler.prototype = 
 
     return this;
   },
 
   _haveProfile: false,
 
   /* nsICommandLineHandler */
   handle : function dch_handle(cmdLine) {
-    // The -url flag is inserted by the operating system when the default
-    // application handler is used. We check for default browser to remove
-    // instances where users explicitly decide to "open with" the browser.
-    // Note that users who launch firefox manually with the -url flag will
-    // get erroneously counted.
-    try {
-      if (cmdLine.findFlag("url", false) &&
-          ShellService.isDefaultBrowser(false, false)) {
-        Services.telemetry.getHistogramById("FX_STARTUP_EXTERNAL_CONTENT_HANDLER").add();
-      }
-    } catch (e) {}
-
     var urilist = [];
 
     if (AppConstants.platform == "win") {
       // If we don't have a profile selected yet (e.g. the Profile Manager is
       // displayed) we will crash if we open an url and then select a profile. To
       // prevent this handle all url command line flags and set the command line's
       // preventDefault to true to prevent the display of the ui. The initial
       // command line will be retained when nsAppRunner calls LaunchChild though

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -5245,23 +5245,16 @@
     "bug_numbers": [1276694],
     "alert_emails": ["gijs@mozilla.com"],
     "expires_in_version": "53",
     "keyed": true,
     "kind": "boolean",
     "releaseChannelCollection": "opt-out",
     "description": "Whether the browser we migrated from was the browser with the most recent data. Keyed by that browser's identifier (e.g. 'ie', 'edge', 'safari', etc.)."
   },
-  "FX_STARTUP_EXTERNAL_CONTENT_HANDLER": {
-    "bug_numbers": [1276027],
-    "alert_emails": ["jaws@mozilla.com"],
-    "expires_in_version": "53",
-    "kind": "count",
-    "description": "Count how often the browser is opened as an external app handler. This is generally used when the browser is set as the default browser."
-  },
   "INPUT_EVENT_RESPONSE_MS": {
     "alert_emails": ["perf-telemetry-alerts@mozilla.com"],
     "bug_numbers": [1235908],
     "expires_in_version": "never",
     "kind": "exponential",
     "high": 10000,
     "n_buckets": 50,
     "description": "Time (ms) from the Input event being created to the end of it being handled"