diff --git a/.eslintignore b/.eslintignore
index 15ed4091741b..9fa022ae27c1 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -183,7 +183,7 @@ services/common/kinto-http-client.js
 services/common/kinto-offline-client.js
 
 # Webpack-bundled library
-services/fxaccounts/FxAccountsPairingChannel.js
+services/fxaccounts/FxAccountsPairingChannel.sys.mjs
 
 # Servo is imported.
 servo/
diff --git a/browser/base/content/test/performance/browser_startup.js b/browser/base/content/test/performance/browser_startup.js
index 9f643dc7ccf1..478dd353e109 100644
--- a/browser/base/content/test/performance/browser_startup.js
+++ b/browser/base/content/test/performance/browser_startup.js
@@ -83,8 +83,8 @@ const startupPhases = {
         "resource://gre/modules/BookmarkHTMLUtils.sys.mjs",
         "resource://gre/modules/Bookmarks.sys.mjs",
         "resource://gre/modules/ContextualIdentityService.sys.mjs",
-        "resource://gre/modules/FxAccounts.jsm",
-        "resource://gre/modules/FxAccountsStorage.jsm",
+        "resource://gre/modules/FxAccounts.sys.mjs",
+        "resource://gre/modules/FxAccountsStorage.sys.mjs",
         "resource://gre/modules/PlacesBackups.sys.mjs",
         "resource://gre/modules/PlacesExpiration.sys.mjs",
         "resource://gre/modules/PlacesSyncUtils.sys.mjs",
diff --git a/services/fxaccounts/Credentials.jsm b/services/fxaccounts/Credentials.sys.mjs
similarity index 95%
rename from services/fxaccounts/Credentials.jsm
rename to services/fxaccounts/Credentials.sys.mjs
index 302caea1a665..155dab3a3070 100644
--- a/services/fxaccounts/Credentials.jsm
+++ b/services/fxaccounts/Credentials.sys.mjs
@@ -9,13 +9,8 @@
  * See https://github.com/mozilla/fxa-auth-server/wiki/onepw-protocol
  */
 
-"use strict";
+import { Log } from "resource://gre/modules/Log.sys.mjs";
 
-var EXPORTED_SYMBOLS = ["Credentials"];
-
-const { Log } = ChromeUtils.importESModule(
-  "resource://gre/modules/Log.sys.mjs"
-);
 const { CryptoUtils } = ChromeUtils.import(
   "resource://services-crypto/utils.js"
 );
@@ -45,7 +40,7 @@ var log = Log.repository.getLogger("Identity.FxAccounts");
 log.level = LOG_LEVEL;
 log.addAppender(new Log.ConsoleAppender(new Log.BasicFormatter()));
 
-var Credentials = Object.freeze({
+export var Credentials = Object.freeze({
   /**
    * Make constants accessible to tests
    */
diff --git a/services/fxaccounts/FxAccounts.jsm b/services/fxaccounts/FxAccounts.sys.mjs
similarity index 99%
rename from services/fxaccounts/FxAccounts.jsm
rename to services/fxaccounts/FxAccounts.sys.mjs
index cf4c1c6c6e78..7d17069f4239 100644
--- a/services/fxaccounts/FxAccounts.jsm
+++ b/services/fxaccounts/FxAccounts.sys.mjs
@@ -1,20 +1,15 @@
 /* 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";
 
-const { PromiseUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/PromiseUtils.sys.mjs"
-);
+import { PromiseUtils } from "resource://gre/modules/PromiseUtils.sys.mjs";
+
 const { CryptoUtils } = ChromeUtils.import(
   "resource://services-crypto/utils.js"
 );
-const { XPCOMUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/XPCOMUtils.sys.mjs"
-);
-const { clearTimeout, setTimeout } = ChromeUtils.importESModule(
-  "resource://gre/modules/Timer.sys.mjs"
-);
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+import { clearTimeout, setTimeout } from "resource://gre/modules/Timer.sys.mjs";
+
 const { FxAccountsStorageManager } = ChromeUtils.import(
   "resource://gre/modules/FxAccountsStorage.jsm"
 );
@@ -129,7 +124,7 @@ XPCOMUtils.defineLazyPreferenceGetter(
 // }
 // If the state has changed between the function being called and the promise
 // being resolved, the .resolve() call will actually be rejected.
-function AccountState(storageManager) {
+export function AccountState(storageManager) {
   this.storageManager = storageManager;
   this.inFlightTokenRequests = new Map();
   this.promiseInitialized = this.storageManager
@@ -375,7 +370,7 @@ function copyObjectProperties(from, to, thisObj, keys) {
  * (although |./mach doc| is broken on windows (bug 1232403) and on Linux for
  * markh (some obscure npm issue he gave up on) - so later...)
  */
-class FxAccounts {
+export class FxAccounts {
   constructor(mocks = null) {
     this._internal = new FxAccountsInternal();
     if (mocks) {
@@ -1645,7 +1640,8 @@ FxAccountsInternal.prototype = {
 };
 
 let fxAccountsSingleton = null;
-function getFxAccountsSingleton() {
+
+export function getFxAccountsSingleton() {
   if (fxAccountsSingleton) {
     return fxAccountsSingleton;
   }
@@ -1660,4 +1656,3 @@ function getFxAccountsSingleton() {
 }
 
 // `AccountState` is exported for tests.
-var EXPORTED_SYMBOLS = ["getFxAccountsSingleton", "FxAccounts", "AccountState"];
diff --git a/services/fxaccounts/FxAccountsClient.jsm b/services/fxaccounts/FxAccountsClient.sys.mjs
similarity index 99%
rename from services/fxaccounts/FxAccountsClient.jsm
rename to services/fxaccounts/FxAccountsClient.sys.mjs
index c81a0cf404ac..8d2a5d50eae6 100644
--- a/services/fxaccounts/FxAccountsClient.jsm
+++ b/services/fxaccounts/FxAccountsClient.sys.mjs
@@ -2,8 +2,6 @@
  * 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/. */
 
-var EXPORTED_SYMBOLS = ["FxAccountsClient"];
-
 const { CommonUtils } = ChromeUtils.import(
   "resource://services-common/utils.js"
 );
@@ -36,7 +34,9 @@ const SIGNUP = "/account/create";
 // Devices older than this many days will not appear in the devices list
 const DEVICES_FILTER_DAYS = 21;
 
-var FxAccountsClient = function(host = Services.prefs.getCharPref(HOST_PREF)) {
+export var FxAccountsClient = function(
+  host = Services.prefs.getCharPref(HOST_PREF)
+) {
   this.host = host;
 
   // The FxA auth server expects requests to certain endpoints to be authorized
diff --git a/services/fxaccounts/FxAccountsCommands.js b/services/fxaccounts/FxAccountsCommands.sys.mjs
similarity index 98%
rename from services/fxaccounts/FxAccountsCommands.js
rename to services/fxaccounts/FxAccountsCommands.sys.mjs
index bd58438db852..0f745f6ee537 100644
--- a/services/fxaccounts/FxAccountsCommands.js
+++ b/services/fxaccounts/FxAccountsCommands.sys.mjs
@@ -2,8 +2,6 @@
  * 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/. */
 
-const EXPORTED_SYMBOLS = ["SendTab", "FxAccountsCommands"];
-
 const {
   COMMAND_SENDTAB,
   COMMAND_SENDTAB_TAIL,
@@ -16,9 +14,8 @@ ChromeUtils.defineModuleGetter(
   "PushCrypto",
   "resource://gre/modules/PushCrypto.jsm"
 );
-const { XPCOMUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/XPCOMUtils.sys.mjs"
-);
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
 const { Observers } = ChromeUtils.import(
   "resource://services-common/observers.js"
 );
@@ -39,7 +36,7 @@ XPCOMUtils.defineLazyPreferenceGetter(
   }
 );
 
-class FxAccountsCommands {
+export class FxAccountsCommands {
   constructor(fxAccountsInternal) {
     this._fxai = fxAccountsInternal;
     this.sendTab = new SendTab(this, fxAccountsInternal);
@@ -248,7 +245,7 @@ class FxAccountsCommands {
  * the push keys to deliver the tabs using same mechanism we use for web-push.
  * However, clients use the send-tab keys for end-to-end encryption.
  */
-class SendTab {
+export class SendTab {
   constructor(commands, fxAccountsInternal) {
     this._commands = commands;
     this._fxai = fxAccountsInternal;
diff --git a/services/fxaccounts/FxAccountsConfig.jsm b/services/fxaccounts/FxAccountsConfig.sys.mjs
similarity index 98%
rename from services/fxaccounts/FxAccountsConfig.jsm
rename to services/fxaccounts/FxAccountsConfig.sys.mjs
index ea485c56d321..8f5d053f0aa3 100644
--- a/services/fxaccounts/FxAccountsConfig.jsm
+++ b/services/fxaccounts/FxAccountsConfig.sys.mjs
@@ -1,8 +1,6 @@
 /* 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";
-var EXPORTED_SYMBOLS = ["FxAccountsConfig"];
 
 const { RESTRequest } = ChromeUtils.import(
   "resource://services-common/rest.js"
@@ -10,9 +8,7 @@ const { RESTRequest } = ChromeUtils.import(
 const { log } = ChromeUtils.import(
   "resource://gre/modules/FxAccountsCommon.js"
 );
-const { XPCOMUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/XPCOMUtils.sys.mjs"
-);
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
 
 const lazy = {};
 
@@ -57,7 +53,7 @@ const CONFIG_PREFS = [
 ];
 const SYNC_PARAM = "sync";
 
-var FxAccountsConfig = {
+export var FxAccountsConfig = {
   async promiseEmailURI(email, entrypoint, extraParams = {}) {
     return this._buildURL("", {
       extraParams: { entrypoint, email, service: SYNC_PARAM, ...extraParams },
diff --git a/services/fxaccounts/FxAccountsDevice.jsm b/services/fxaccounts/FxAccountsDevice.sys.mjs
similarity index 99%
rename from services/fxaccounts/FxAccountsDevice.jsm
rename to services/fxaccounts/FxAccountsDevice.sys.mjs
index e2d945e3399b..ba5ebd0025f4 100644
--- a/services/fxaccounts/FxAccountsDevice.jsm
+++ b/services/fxaccounts/FxAccountsDevice.sys.mjs
@@ -1,11 +1,8 @@
 /* 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";
 
-const { XPCOMUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/XPCOMUtils.sys.mjs"
-);
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
 
 const {
   log,
@@ -57,7 +54,7 @@ function sanitizeDeviceName(name) {
 }
 
 // Everything to do with FxA devices.
-class FxAccountsDevice {
+export class FxAccountsDevice {
   constructor(fxai) {
     this._fxai = fxai;
     this._deviceListCache = null;
@@ -653,5 +650,3 @@ FxAccountsDevice.prototype.QueryInterface = ChromeUtils.generateQI([
 function urlsafeBase64Encode(buffer) {
   return ChromeUtils.base64URLEncode(new Uint8Array(buffer), { pad: false });
 }
-
-var EXPORTED_SYMBOLS = ["FxAccountsDevice"];
diff --git a/services/fxaccounts/FxAccountsKeys.jsm b/services/fxaccounts/FxAccountsKeys.sys.mjs
similarity index 99%
rename from services/fxaccounts/FxAccountsKeys.jsm
rename to services/fxaccounts/FxAccountsKeys.sys.mjs
index e4cf5339ed30..97f86ab76994 100644
--- a/services/fxaccounts/FxAccountsKeys.jsm
+++ b/services/fxaccounts/FxAccountsKeys.sys.mjs
@@ -1,11 +1,9 @@
 /* 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";
 
-const { PromiseUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/PromiseUtils.sys.mjs"
-);
+import { PromiseUtils } from "resource://gre/modules/PromiseUtils.sys.mjs";
+
 const { CommonUtils } = ChromeUtils.import(
   "resource://services-common/utils.js"
 );
@@ -56,7 +54,7 @@ const DEPRECATED_KEY_SCOPES = [DEPRECATED_SCOPE_ECOSYSTEM_TELEMETRY];
  * possible.  We intend to remove support for Firefox ever directly handling `kB`
  * at some point in the future.
  */
-class FxAccountsKeys {
+export class FxAccountsKeys {
   constructor(fxAccountsInternal) {
     this._fxai = fxAccountsInternal;
   }
@@ -749,5 +747,3 @@ class FxAccountsKeys {
     return CryptoUtils.digestBytes(bytes, hasher);
   }
 }
-
-var EXPORTED_SYMBOLS = ["FxAccountsKeys"];
diff --git a/services/fxaccounts/FxAccountsPairing.jsm b/services/fxaccounts/FxAccountsPairing.sys.mjs
similarity index 98%
rename from services/fxaccounts/FxAccountsPairing.jsm
rename to services/fxaccounts/FxAccountsPairing.sys.mjs
index 371e792f4980..2f0d487b00ee 100644
--- a/services/fxaccounts/FxAccountsPairing.jsm
+++ b/services/fxaccounts/FxAccountsPairing.sys.mjs
@@ -2,8 +2,6 @@
 // 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";
-
 const {
   log,
   PREF_REMOTE_PAIRING_URI,
@@ -17,9 +15,8 @@ const { getFxAccountsSingleton, FxAccounts } = ChromeUtils.import(
   "resource://gre/modules/FxAccounts.jsm"
 );
 const fxAccounts = getFxAccountsSingleton();
-const { setTimeout, clearTimeout } = ChromeUtils.importESModule(
-  "resource://gre/modules/Timer.sys.mjs"
-);
+import { setTimeout, clearTimeout } from "resource://gre/modules/Timer.sys.mjs";
+
 ChromeUtils.import("resource://services-common/utils.js");
 const lazy = {};
 ChromeUtils.defineESModuleGetters(lazy, {
@@ -173,7 +170,8 @@ class Errored extends State {
 }
 
 const flows = new Map();
-class FxAccountsPairingFlow {
+
+export class FxAccountsPairingFlow {
   static get(channelId) {
     return flows.get(channelId);
   }
@@ -518,5 +516,3 @@ class FxAccountsPairingFlow {
     );
   }
 }
-
-const EXPORTED_SYMBOLS = ["FxAccountsPairingFlow"];
diff --git a/services/fxaccounts/FxAccountsPairingChannel.js b/services/fxaccounts/FxAccountsPairingChannel.sys.mjs
similarity index 99%
rename from services/fxaccounts/FxAccountsPairingChannel.js
rename to services/fxaccounts/FxAccountsPairingChannel.sys.mjs
index 0e9597d6fb18..cb6d3fdb91a4 100644
--- a/services/fxaccounts/FxAccountsPairingChannel.js
+++ b/services/fxaccounts/FxAccountsPairingChannel.sys.mjs
@@ -22,15 +22,14 @@
 // from Firefox browser code, hence the presence of these privileged browser APIs.
 // If you're trying to use this from ordinary web content you're in for a bad time.
 
-const {setTimeout} = ChromeUtils.importESModule("resource://gre/modules/Timer.sys.mjs");
+import { setTimeout } from "resource://gre/modules/Timer.sys.mjs";
+
 // We cannot use WebSocket from chrome code without a window,
 // see https://bugzilla.mozilla.org/show_bug.cgi?id=784686
 const browser = Services.appShell.createWindowlessBrowser(true);
 const {WebSocket} = browser.document.ownerGlobal;
 
-const EXPORTED_SYMBOLS = ["FxAccountsPairingChannel"];
-
-var FxAccountsPairingChannel =
+export var FxAccountsPairingChannel =
 /******/ (function(modules) { // webpackBootstrap
 /******/ 	// The module cache
 /******/ 	var installedModules = {};
@@ -704,7 +703,7 @@ async function verifyHmac(keyBytes, signature, message) {
     hash: { name: 'SHA-256' },
     name: 'HMAC',
   }, false, ['verify']);
-  if (! await crypto.subtle.verify({ name: 'HMAC' }, key, signature, message)) {
+  if (! (await crypto.subtle.verify({ name: 'HMAC' }, key, signature, message))) {
     // Yes, we really do throw 'decrypt_error' when failing to verify a HMAC,
     // and a 'bad_record_mac' error when failing to decrypt.
     throw new TLSError(ALERT_DESCRIPTION.DECRYPT_ERROR);
diff --git a/services/fxaccounts/FxAccountsProfile.jsm b/services/fxaccounts/FxAccountsProfile.sys.mjs
similarity index 98%
rename from services/fxaccounts/FxAccountsProfile.jsm
rename to services/fxaccounts/FxAccountsProfile.sys.mjs
index 49594d992c6e..3b860ad3f4f1 100644
--- a/services/fxaccounts/FxAccountsProfile.jsm
+++ b/services/fxaccounts/FxAccountsProfile.sys.mjs
@@ -2,8 +2,6 @@
  * 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";
-
 /**
  * Firefox Accounts Profile helper.
  *
@@ -12,8 +10,6 @@
  * the user's profile in open browser tabs, and cacheing/invalidating profile data.
  */
 
-var EXPORTED_SYMBOLS = ["FxAccountsProfile"];
-
 const { ON_PROFILE_CHANGE_NOTIFICATION, log } = ChromeUtils.import(
   "resource://gre/modules/FxAccountsCommon.js"
 );
@@ -30,7 +26,7 @@ ChromeUtils.defineModuleGetter(
   "resource://gre/modules/FxAccountsProfileClient.jsm"
 );
 
-var FxAccountsProfile = function(options = {}) {
+export var FxAccountsProfile = function(options = {}) {
   this._currentFetchPromise = null;
   this._cachedAt = 0; // when we saved the cached version.
   this._isNotifying = false; // are we sending a notification?
diff --git a/services/fxaccounts/FxAccountsProfileClient.jsm b/services/fxaccounts/FxAccountsProfileClient.sys.mjs
similarity index 97%
rename from services/fxaccounts/FxAccountsProfileClient.jsm
rename to services/fxaccounts/FxAccountsProfileClient.sys.mjs
index c554699ef58b..0ba2c71e7857 100644
--- a/services/fxaccounts/FxAccountsProfileClient.jsm
+++ b/services/fxaccounts/FxAccountsProfileClient.sys.mjs
@@ -7,11 +7,6 @@
  */
 "use strict;";
 
-var EXPORTED_SYMBOLS = [
-  "FxAccountsProfileClient",
-  "FxAccountsProfileClientError",
-];
-
 const {
   ERRNO_NETWORK,
   ERRNO_PARSE,
@@ -44,7 +39,7 @@ const { RESTRequest } = ChromeUtils.import(
  *   The bearer token to access the profile server
  * @constructor
  */
-var FxAccountsProfileClient = function(options) {
+export var FxAccountsProfileClient = function(options) {
   if (!options || !options.serverURL) {
     throw new Error("Missing 'serverURL' configuration option");
   }
@@ -244,7 +239,7 @@ FxAccountsProfileClient.prototype = {
  *          Error message
  * @constructor
  */
-var FxAccountsProfileClientError = function(details) {
+export var FxAccountsProfileClientError = function(details) {
   details = details || {};
 
   this.name = "FxAccountsProfileClientError";
diff --git a/services/fxaccounts/FxAccountsPush.jsm b/services/fxaccounts/FxAccountsPush.sys.mjs
similarity index 99%
rename from services/fxaccounts/FxAccountsPush.jsm
rename to services/fxaccounts/FxAccountsPush.sys.mjs
index 32160135cca1..05b56e61aa3f 100644
--- a/services/fxaccounts/FxAccountsPush.jsm
+++ b/services/fxaccounts/FxAccountsPush.sys.mjs
@@ -26,7 +26,7 @@ const {
  *        Object, custom options that used for testing
  * @constructor
  */
-function FxAccountsPushService(options = {}) {
+export function FxAccountsPushService(options = {}) {
   this.log = log;
 
   if (options.log) {
@@ -312,5 +312,3 @@ FxAccountsPushService.prototype = {
     });
   },
 };
-
-var EXPORTED_SYMBOLS = ["FxAccountsPushService"];
diff --git a/services/fxaccounts/FxAccountsStorage.jsm b/services/fxaccounts/FxAccountsStorage.sys.mjs
similarity index 98%
rename from services/fxaccounts/FxAccountsStorage.jsm
rename to services/fxaccounts/FxAccountsStorage.sys.mjs
index 7b1afba4f6c9..a3222275f1b2 100644
--- a/services/fxaccounts/FxAccountsStorage.jsm
+++ b/services/fxaccounts/FxAccountsStorage.sys.mjs
@@ -1,14 +1,6 @@
 /* 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";
-
-var EXPORTED_SYMBOLS = [
-  "FxAccountsStorageManagerCanStoreField",
-  "FxAccountsStorageManager",
-  // Exported for tests.
-  "LoginManagerStorage",
-];
 
 const {
   DATA_FORMAT_VERSION,
@@ -22,7 +14,7 @@ const {
 
 // A helper function so code can check what fields are able to be stored by
 // the storage manager without having a reference to a manager instance.
-function FxAccountsStorageManagerCanStoreField(fieldName) {
+export function FxAccountsStorageManagerCanStoreField(fieldName) {
   return (
     FXA_PWDMGR_PLAINTEXT_FIELDS.has(fieldName) ||
     FXA_PWDMGR_SECURE_FIELDS.has(fieldName)
@@ -30,7 +22,7 @@ function FxAccountsStorageManagerCanStoreField(fieldName) {
 }
 
 // The storage manager object.
-var FxAccountsStorageManager = function(options = {}) {
+export var FxAccountsStorageManager = function(options = {}) {
   this.options = {
     filename: options.filename || DEFAULT_STORAGE_FILENAME,
     baseDir: options.baseDir || Services.dirsvc.get("ProfD", Ci.nsIFile).path,
@@ -475,6 +467,7 @@ JSONStorage.prototype = {
 };
 
 function StorageLockedError() {}
+
 /**
  * LoginManagerStorage constructor that creates instances that set/get
  * data stored securely in the nsILoginManager.
@@ -482,7 +475,7 @@ function StorageLockedError() {}
  * @return instance
  */
 
-function LoginManagerStorage() {}
+export function LoginManagerStorage() {}
 
 LoginManagerStorage.prototype = {
   STORAGE_LOCKED: StorageLockedError,
diff --git a/services/fxaccounts/FxAccountsTelemetry.jsm b/services/fxaccounts/FxAccountsTelemetry.sys.mjs
similarity index 97%
rename from services/fxaccounts/FxAccountsTelemetry.jsm
rename to services/fxaccounts/FxAccountsTelemetry.sys.mjs
index 1d8cb6fc6f21..b2b9f6ca3682 100644
--- a/services/fxaccounts/FxAccountsTelemetry.jsm
+++ b/services/fxaccounts/FxAccountsTelemetry.sys.mjs
@@ -2,16 +2,12 @@
  * 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";
-
 // FxA Telemetry support. For hysterical raisins, the actual implementation
 // is inside "sync". We should move the core implementation somewhere that's
 // sanely shared (eg, services-common?), but let's wait and see where we end up
 // first...
 
-const { XPCOMUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/XPCOMUtils.sys.mjs"
-);
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
 
 const lazy = {};
 
@@ -34,7 +30,7 @@ XPCOMUtils.defineLazyPreferenceGetter(
   ""
 );
 
-class FxAccountsTelemetry {
+export class FxAccountsTelemetry {
   constructor(fxai) {
     this._fxai = fxai;
     Services.telemetry.setEventRecordingEnabled("fxa", true);
@@ -176,5 +172,3 @@ class FxAccountsTelemetry {
     }
   }
 }
-
-var EXPORTED_SYMBOLS = ["FxAccountsTelemetry"];
diff --git a/services/fxaccounts/FxAccountsWebChannel.jsm b/services/fxaccounts/FxAccountsWebChannel.sys.mjs
similarity index 98%
rename from services/fxaccounts/FxAccountsWebChannel.jsm
rename to services/fxaccounts/FxAccountsWebChannel.sys.mjs
index 50c85c953683..6e9faadc493f 100644
--- a/services/fxaccounts/FxAccountsWebChannel.jsm
+++ b/services/fxaccounts/FxAccountsWebChannel.sys.mjs
@@ -1,7 +1,6 @@
 /* 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";
 
 /**
  * Firefox Accounts Web Channel.
@@ -10,16 +9,8 @@
  * about account state changes.
  */
 
-var EXPORTED_SYMBOLS = [
-  "EnsureFxAccountsWebChannel",
-  // These are exported for tests.
-  "FxAccountsWebChannel",
-  "FxAccountsWebChannelHelpers",
-];
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
 
-const { XPCOMUtils } = ChromeUtils.importESModule(
-  "resource://gre/modules/XPCOMUtils.sys.mjs"
-);
 const {
   COMMAND_PROFILE_CHANGE,
   COMMAND_LOGIN,
@@ -141,7 +132,7 @@ function getErrorDetails(error) {
  *     Helpers functions. Should only be passed in for testing.
  * @constructor
  */
-function FxAccountsWebChannel(options) {
+export function FxAccountsWebChannel(options) {
   if (!options) {
     throw new Error("Missing configuration options");
   }
@@ -406,7 +397,7 @@ FxAccountsWebChannel.prototype = {
   },
 };
 
-function FxAccountsWebChannelHelpers(options) {
+export function FxAccountsWebChannelHelpers(options) {
   options = options || {};
 
   this._fxAccounts = options.fxAccounts || lazy.fxAccounts;
@@ -743,12 +734,13 @@ FxAccountsWebChannelHelpers.prototype = {
 };
 
 var singleton;
+
 // The entry-point for this module, which ensures only one of our channels is
 // ever created - we require this because the WebChannel is global in scope
 // (eg, it uses the observer service to tell interested parties of interesting
 // things) and allowing multiple channels would cause such notifications to be
 // sent multiple times.
-var EnsureFxAccountsWebChannel = () => {
+export var EnsureFxAccountsWebChannel = () => {
   let contentUri = Services.urlFormatter.formatURLPref(
     "identity.fxaccounts.remote.root"
   );
diff --git a/services/fxaccounts/components.conf b/services/fxaccounts/components.conf
index 74fb0bcf3eb1..992c88d0cbf8 100644
--- a/services/fxaccounts/components.conf
+++ b/services/fxaccounts/components.conf
@@ -8,7 +8,7 @@ Classes = [
     {
         'cid': '{1b7db999-2ecd-4abf-bb95-a726896798ca}',
         'contract_ids': ['@mozilla.org/fxaccounts/push;1'],
-        'jsm': 'resource://gre/modules/FxAccountsPush.jsm',
+        'esModule': 'resource://gre/modules/FxAccountsPush.sys.mjs',
         'constructor': 'FxAccountsPushService',
         'processes': ProcessSelector.MAIN_PROCESS_ONLY,
         'categories': {'push': 'chrome://fxa-device-update'},
diff --git a/services/fxaccounts/moz.build b/services/fxaccounts/moz.build
index 57cfb77e9bde..a99a5b0d591e 100644
--- a/services/fxaccounts/moz.build
+++ b/services/fxaccounts/moz.build
@@ -14,22 +14,22 @@ BROWSER_CHROME_MANIFESTS += ["tests/browser/browser.ini"]
 XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.ini"]
 
 EXTRA_JS_MODULES += [
-    "Credentials.jsm",
-    "FxAccounts.jsm",
-    "FxAccountsClient.jsm",
-    "FxAccountsCommands.js",
+    "Credentials.sys.mjs",
+    "FxAccounts.sys.mjs",
+    "FxAccountsClient.sys.mjs",
+    "FxAccountsCommands.sys.mjs",
     "FxAccountsCommon.js",
-    "FxAccountsConfig.jsm",
-    "FxAccountsDevice.jsm",
-    "FxAccountsKeys.jsm",
-    "FxAccountsPairing.jsm",
-    "FxAccountsPairingChannel.js",
-    "FxAccountsProfile.jsm",
-    "FxAccountsProfileClient.jsm",
-    "FxAccountsPush.jsm",
-    "FxAccountsStorage.jsm",
-    "FxAccountsTelemetry.jsm",
-    "FxAccountsWebChannel.jsm",
+    "FxAccountsConfig.sys.mjs",
+    "FxAccountsDevice.sys.mjs",
+    "FxAccountsKeys.sys.mjs",
+    "FxAccountsPairing.sys.mjs",
+    "FxAccountsPairingChannel.sys.mjs",
+    "FxAccountsProfile.sys.mjs",
+    "FxAccountsProfileClient.sys.mjs",
+    "FxAccountsPush.sys.mjs",
+    "FxAccountsStorage.sys.mjs",
+    "FxAccountsTelemetry.sys.mjs",
+    "FxAccountsWebChannel.sys.mjs",
 ]
 
 XPCOM_MANIFESTS += [