--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1779,8 +1779,11 @@ pref("prio.publicKeyB", "26E6674E65425B8
 #if defined(NIGHTLY_BUILD) && defined(MOZ_LIBPRIO)
 pref("prio.enabled", true);
 #endif
 
 #ifdef NIGHTLY_BUILD
 pref("browser.fastblock.enabled", true);
 #endif
 
+// Telemetry Coverage is disabled by default.
+pref("toolkit.telemetry.coverage.enabled", false);
+pref("toolkit.telemetry.coverage.endpoint.base", "https://telemetry-coverage.mozilla.org");

--- a/testing/profiles/common/user.js
+++ b/testing/profiles/common/user.js
@@ -44,8 +44,9 @@ user_pref("xpinstall.signatures.required
 // Prevent Remote Settings to issue non local connections.
 user_pref("services.settings.server", "http://localhost/remote-settings-dummy/v1");
 // Ensure autoplay is enabled for all platforms.
 user_pref("media.autoplay.default", 0); // 0=Allowed, 1=Blocked, 2=Prompt
 user_pref("media.autoplay.enabled.user-gestures-needed", true);
 user_pref("media.autoplay.ask-permission", false);
 user_pref("media.autoplay.block-webaudio", false);
 user_pref("media.allowed-to-play.enabled", true);
+user_pref("toolkit.telemetry.coverage.endpoint.base", "http://localhost");

--- a/toolkit/components/telemetry/app/TelemetryController.jsm
+++ b/toolkit/components/telemetry/app/TelemetryController.jsm
@@ -47,16 +47,17 @@ const REASON_GATHER_PAYLOAD = "gather-pa
 const REASON_GATHER_SUBSESSION_PAYLOAD = "gather-subsession-payload";
 
 XPCOMUtils.defineLazyServiceGetter(this, "Telemetry",
                                    "@mozilla.org/base/telemetry;1",
                                    "nsITelemetry");
 
 XPCOMUtils.defineLazyModuleGetters(this, {
   ClientID: "resource://gre/modules/ClientID.jsm",
+  CoveragePing: "resource://gre/modules/CoveragePing.jsm",
   AsyncShutdown: "resource://gre/modules/AsyncShutdown.jsm",
   TelemetryStorage: "resource://gre/modules/TelemetryStorage.jsm",
   TelemetryEnvironment: "resource://gre/modules/TelemetryEnvironment.jsm",
   TelemetryArchive: "resource://gre/modules/TelemetryArchive.jsm",
   TelemetrySession: "resource://gre/modules/TelemetrySession.jsm",
   MemoryTelemetry: "resource://gre/modules/MemoryTelemetry.jsm",
   TelemetrySend: "resource://gre/modules/TelemetrySend.jsm",
   TelemetryReportingPolicy: "resource://gre/modules/TelemetryReportingPolicy.jsm",
@@ -692,16 +693,19 @@ var Impl = {
         // in the future.
         TelemetryStorage.removeFHRDatabase();
 
         // The init sequence is forced to run on shutdown for short sessions and
         // we don't want to start TelemetryModules as the timer registration will fail.
         if (!this._shuttingDown) {
           // Report the modules loaded in the Firefox process.
           TelemetryModules.start();
+
+          // Send telemetry coverage ping.
+          await CoveragePing.startup();
         }
 
         TelemetryEventPing.startup();
 
         this._delayedInitTaskDeferred.resolve();
       } catch (e) {
         this._delayedInitTaskDeferred.reject(e);
       } finally {

new file mode 100644
--- /dev/null
+++ b/toolkit/components/telemetry/docs/data/coverage-ping.rst
@@ -0,0 +1,40 @@
+
+"coverage" ping
+=============
+
+This ping is not enabled by default. When enabled, a ping is generated a total of once per profile, as a diagnostic tool
+to determine whether Telemetry is working for users.
+
+This ping contains no client id and no environment data.
+
+You can find more background information in `this blog post <https://blog.mozilla.org/data/2018/08/20/effectively-measuring-search-in-firefox/>`_.
+
+Structure:
+
+.. code-block:: js
+
+    {
+      "appVersion": "63.0a1",
+      "appUpdateChannel": "nightly",
+      "osName": "Darwin",
+      "osVersion": "17.7.0",
+      "telemetryEnabled": 1
+    }
+
+Expected behaviours
+-------------------
+The following is a list of expected behaviours for the ``coverage`` ping:
+
+- The ping will only be sent once per ping version, per profile.
+- If sending the ping fails, it will be retried on startup.
+- A totally arbitrary UUID is generated on first run on a new profile, to use for filtering duplicates.
+- The ping is sent to a different endpoint not using existing Telemetry.
+- The ping does not honor the Telemetry enabled preference, but provides its own opt-out preference: `toolkit.telemetry.coverage.opt-out`.
+- The ping is disabled by default. It is intended to be enabled for users on an experimental basis using the preference `toolkit.telemetry.coverage.enabled`.
+
+Version History
+---------------
+
+- Firefox 64:
+
+  - "coverage" ping shipped (`bug 1492656 <https://bugzilla.mozilla.org/show_bug.cgi?id=1492656>`_).

--- a/toolkit/components/telemetry/moz.build
+++ b/toolkit/components/telemetry/moz.build
@@ -95,16 +95,17 @@ EXTRA_JS_MODULES += [
     'app/TelemetrySend.jsm',
     'app/TelemetryStopwatch.jsm',
     'app/TelemetryStorage.jsm',
     'app/TelemetryTimestamps.jsm',
     'app/TelemetryUtils.jsm',
     'other/GCTelemetry.jsm',
     'other/MemoryTelemetry.jsm',
     'other/UITelemetry.jsm',
+    'pings/CoveragePing.jsm',
     'pings/EventPing.jsm',
     'pings/HealthPing.jsm',
     'pings/ModulesPing.jsm',
     'pings/TelemetrySession.jsm',
     'pings/UpdatePing.jsm',
 ]
 
 TESTING_JS_MODULES += [

new file mode 100644
--- /dev/null
+++ b/toolkit/components/telemetry/pings/CoveragePing.jsm
@@ -0,0 +1,154 @@
+/* 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/. */
+"use strict";
+
+ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+ChromeUtils.defineModuleGetter(this,
+  "CommonUtils", "resource://services-common/utils.js");
+ChromeUtils.defineModuleGetter(this,
+  "Log", "resource://gre/modules/Log.jsm");
+ChromeUtils.defineModuleGetter(this,
+  "PromiseUtils", "resource://gre/modules/PromiseUtils.jsm");
+ChromeUtils.defineModuleGetter(this,
+  "ServiceRequest", "resource://gre/modules/ServiceRequest.jsm");
+ChromeUtils.defineModuleGetter(this,
+  "UpdateUtils", "resource://gre/modules/UpdateUtils.jsm");
+
+var EXPORTED_SYMBOLS = ["CoveragePing"];
+
+const COVERAGE_VERSION = "2";
+
+const COVERAGE_ENABLED_PREF = "toolkit.telemetry.coverage.enabled";
+const LOG_LEVEL_PREF = "toolkit.telemetry.coverage.log-level";
+const OPT_OUT_PREF = "toolkit.telemetry.coverage.opt-out";
+const ALREADY_RUN_PREF = `toolkit.telemetry.coverage.already-run.v${COVERAGE_VERSION}`;
+const COVERAGE_UUID_PREF = `toolkit.telemetry.coverage.uuid.v${COVERAGE_VERSION}`;
+const TELEMETRY_ENABLED_PREF = "datareporting.healthreport.uploadEnabled";
+const REPORTING_ENDPOINT_BASE_PREF = `toolkit.telemetry.coverage.endpoint.base`;
+const REPORTING_ENDPOINT = "submit/coverage/coverage";
+const PING_SUBMISSION_TIMEOUT = 30 * 1000; // 30 seconds
+
+const log = Log.repository.getLogger("Telemetry::CoveragePing");
+log.level = Services.prefs.getIntPref(LOG_LEVEL_PREF, Log.Level.Error);
+log.addAppender(new Log.ConsoleAppender(new Log.BasicFormatter()));
+
+var CoveragePing = Object.freeze({
+  async startup() {
+    if (!Services.prefs.getCharPref(REPORTING_ENDPOINT_BASE_PREF, null)) {
+      log.error("no endpoint base set");
+      return;
+    }
+
+    if (!Services.prefs.getBoolPref(COVERAGE_ENABLED_PREF)) {
+      log.debug("coverage not enabled");
+      return;
+    }
+
+    if (Services.prefs.getBoolPref(OPT_OUT_PREF, false)) {
+      log.debug("user has set opt-out pref");
+      return;
+    }
+
+    if (Services.prefs.getBoolPref(ALREADY_RUN_PREF, false)) {
+      log.debug("already run on this profile");
+      return;
+    }
+
+    try {
+      await this.reportTelemetrySetting();
+    } catch (e) {
+      log.error("unable to upload payload", e);
+    }
+  },
+
+  // NOTE - this does not use existing Telemetry code or honor Telemetry opt-out prefs,
+  // by design. It also sends no identifying data like the client ID. See the "coverage ping"
+  // documentation for details.
+  reportTelemetrySetting() {
+    const enabled = Services.prefs.getBoolPref(TELEMETRY_ENABLED_PREF, false);
+
+    const payload = {
+      "appVersion": Services.appinfo.version,
+      "appUpdateChannel": UpdateUtils.getUpdateChannel(false),
+      "osName": Services.sysinfo.getProperty("name"),
+      "osVersion": Services.sysinfo.getProperty("version"),
+      "telemetryEnabled": enabled,
+    };
+
+    let cachedUuid = Services.prefs.getCharPref(COVERAGE_UUID_PREF, null);
+    if (!cachedUuid) {
+      // Totally random UUID, just for detecting duplicates.
+      cachedUuid = CommonUtils.generateUUID();
+      Services.prefs.setCharPref(COVERAGE_UUID_PREF, cachedUuid);
+    }
+
+    let reportingEndpointBase = Services.prefs.getCharPref(REPORTING_ENDPOINT_BASE_PREF, null);
+
+    let endpoint = `${reportingEndpointBase}/${REPORTING_ENDPOINT}/${COVERAGE_VERSION}/${cachedUuid}`;
+
+    log.debug(`putting to endpoint ${endpoint} with payload:`, payload);
+
+    let deferred = PromiseUtils.defer();
+
+    let request = new ServiceRequest({mozAnon: true});
+    request.mozBackgroundRequest = true;
+    request.timeout = PING_SUBMISSION_TIMEOUT;
+
+    request.open("PUT", endpoint, true);
+    request.overrideMimeType("text/plain");
+    request.setRequestHeader("Content-Type", "application/json; charset=UTF-8");
+    request.setRequestHeader("Date", new Date().toUTCString());
+
+    // Prevent the request channel from running though URLClassifier (bug 1296802)
+    request.channel.loadFlags &= ~Ci.nsIChannel.LOAD_CLASSIFY_URI;
+
+    let errorhandler = (event) => {
+      let failure = event.type;
+      log.error(`error making request to ${endpoint}: ${failure}`);
+      deferred.reject(event);
+    };
+
+    request.onerror = errorhandler;
+    request.ontimeout = errorhandler;
+    request.onabort = errorhandler;
+
+    request.onloadend = (event) => {
+      let status = request.status;
+      let statusClass = status - (status % 100);
+      let success = false;
+
+      if (statusClass === 200) {
+        // We can treat all 2XX as success.
+        log.info(`successfully submitted, status: ${status}`);
+        success = true;
+      } else if (statusClass === 400) {
+        // 4XX means that something with the request was broken.
+
+        // TODO: we should handle this better, but for now we should avoid resubmitting
+        // broken requests by pretending success.
+        success = true;
+        log.error(`error submitting to ${endpoint}, status: ${status} - ping request broken?`);
+      } else if (statusClass === 500) {
+        // 5XX means there was a server-side error and we should try again later.
+        log.error(`error submitting to ${endpoint}, status: ${status} - server error, should retry later`);
+      } else {
+        // We received an unexpected status code.
+        log.error(`error submitting to ${endpoint}, status: ${status}, type: ${event.type}`);
+      }
+
+      if (success) {
+        Services.prefs.setBoolPref(ALREADY_RUN_PREF, true);
+        log.debug(`result from PUT: ${request.responseText}`);
+        deferred.resolve();
+      } else {
+        deferred.reject(event);
+      }
+    };
+
+    request.send(JSON.stringify(payload));
+
+    return deferred.promise;
+  },
+});

new file mode 100644
--- /dev/null
+++ b/toolkit/components/telemetry/tests/unit/test_CoveragePing.js
@@ -0,0 +1,104 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.import("resource://gre/modules/CoveragePing.jsm");
+ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+ChromeUtils.import("resource://testing-common/httpd.js");
+
+
+const COVERAGE_VERSION = "2";
+
+const COVERAGE_ENABLED_PREF = "toolkit.telemetry.coverage.enabled";
+const OPT_OUT_PREF = "toolkit.telemetry.coverage.opt-out";
+const ALREADY_RUN_PREF = `toolkit.telemetry.coverage.already-run.v${COVERAGE_VERSION}`;
+const COVERAGE_UUID_PREF = `toolkit.telemetry.coverage.uuid.v${COVERAGE_VERSION}`;
+const TELEMETRY_ENABLED_PREF = "datareporting.healthreport.uploadEnabled";
+const REPORTING_ENDPOINT_BASE_PREF = "toolkit.telemetry.coverage.endpoint.base";
+const REPORTING_ENDPOINT = "submit/coverage/coverage";
+
+Services.prefs.setIntPref("toolkit.telemetry.coverage.log-level", 20);
+
+add_task(async function setup() {
+  let uuid = "test123";
+  Services.prefs.setCharPref(COVERAGE_UUID_PREF, uuid);
+
+  const server = new HttpServer();
+  server.start(-1);
+  const serverPort = server.identity.primaryPort;
+
+  Services.prefs.setCharPref(REPORTING_ENDPOINT_BASE_PREF, `http://localhost:${serverPort}`);
+
+  server.registerPathHandler(`/${REPORTING_ENDPOINT}/${COVERAGE_VERSION}/${uuid}`, (request, response) => {
+    equal(request.method, "PUT");
+    let telemetryEnabled = Services.prefs.getBoolPref(TELEMETRY_ENABLED_PREF, false);
+
+    let requestBody = NetUtil.readInputStreamToString(request.bodyInputStream,
+      request.bodyInputStream.available());
+
+    let resultObj = JSON.parse(requestBody);
+
+    deepEqual(Object.keys(resultObj), [
+      "appUpdateChannel", "osName", "osVersion", "telemetryEnabled",
+    ]);
+
+    if (telemetryEnabled) {
+      ok(resultObj.telemetryEnabled);
+    } else {
+      ok(!resultObj.telemetryEnabled);
+    }
+
+    const response_body = "OK";
+    response.bodyOutputStream.write(response_body, response_body.length);
+    server.stop();
+  });
+
+  // Trigger a proper telemetry init.
+  do_get_profile(true);
+  // Make sure we don't generate unexpected pings due to pref changes.
+  await setEmptyPrefWatchlist();
+
+  await TelemetryController.testSetup();
+});
+
+add_task(async function test_prefs() {
+  // Telemetry reporting setting does not control this ping, but it
+  // reported by this ping.
+  Services.prefs.setBoolPref(TELEMETRY_ENABLED_PREF, false);
+
+  // should not run if enabled pref is false
+  Services.prefs.setBoolPref(COVERAGE_ENABLED_PREF, false);
+  Services.prefs.setBoolPref(ALREADY_RUN_PREF, false);
+  Services.prefs.setBoolPref(OPT_OUT_PREF, false);
+
+  await TelemetryController.testReset();
+
+  let alreadyRun = Services.prefs.getBoolPref(ALREADY_RUN_PREF, false);
+  ok(!alreadyRun, "should not have run with enabled pref false");
+
+  // should not run if opt-out pref is true
+  Services.prefs.setBoolPref(COVERAGE_ENABLED_PREF, true);
+  Services.prefs.setBoolPref(ALREADY_RUN_PREF, false);
+  Services.prefs.setBoolPref(OPT_OUT_PREF, true);
+
+  await TelemetryController.testReset();
+
+  // should run if opt-out pref is false and coverage is enabled
+  Services.prefs.setBoolPref(COVERAGE_ENABLED_PREF, true);
+  Services.prefs.setBoolPref(ALREADY_RUN_PREF, false);
+  Services.prefs.setBoolPref(OPT_OUT_PREF, false);
+
+  await TelemetryController.testReset();
+
+  // the telemetry setting should be set correctly
+  Services.prefs.setBoolPref(TELEMETRY_ENABLED_PREF, true);
+
+  await TelemetryController.testReset();
+
+  alreadyRun = Services.prefs.getBoolPref(ALREADY_RUN_PREF, false);
+
+  ok(alreadyRun, "should run if no opt-out and enabled");
+});
+

--- a/toolkit/components/telemetry/tests/unit/xpcshell.ini
+++ b/toolkit/components/telemetry/tests/unit/xpcshell.ini
@@ -86,8 +86,10 @@ skip-if = os == "android" # Disabled due
 [test_ModulesPing.js]
 [test_PingSender.js]
 skip-if = (os == "android") || (os == "linux" && bits == 32)
 [test_TelemetryGC.js]
 [test_TelemetryAndroidEnvironment.js]
 [test_TelemetryUtils.js]
 [test_EventPing.js]
 [test_EventPing_disabled.js]
+tags = coverage
+[test_CoveragePing.js]