diff --git a/.prettierignore b/.prettierignore
index 4ba482e89873..6e7a4422954c 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -30,7 +30,6 @@ modules/libpref/test/unit/data/testPrefSticky.js
 modules/libpref/test/unit/extdata/testExt.js
 remote/pref/remote.js
 services/sync/tests/unit/prefs_test_prefs_store.js
-testing/marionette/prefs/marionette.js
 
 # Ignore testing pref files which aren't parsed normally.
 testing/profiles/**/user.js
diff --git a/browser/installer/package-manifest.in b/browser/installer/package-manifest.in
index 98b7f1c7f4f7..abcf9968d4cc 100644
--- a/browser/installer/package-manifest.in
+++ b/browser/installer/package-manifest.in
@@ -207,7 +207,6 @@
 @RESPATH@/chrome/marionette.manifest
 @RESPATH@/components/marionette.manifest
 @RESPATH@/components/marionette.js
-@RESPATH@/defaults/pref/marionette.js
 #endif
 
 #if defined(ENABLE_TESTS) && defined(MOZ_DEBUG)
diff --git a/mobile/android/installer/package-manifest.in b/mobile/android/installer/package-manifest.in
index 162728fabe37..49f33a4f0336 100644
--- a/mobile/android/installer/package-manifest.in
+++ b/mobile/android/installer/package-manifest.in
@@ -275,7 +275,6 @@
 @BINPATH@/chrome/marionette.manifest
 @BINPATH@/components/marionette.manifest
 @BINPATH@/components/marionette.js
-@BINPATH@/@PREF_DIR@/marionette.js
 #endif
 
 #ifdef PKG_LOCALE_MANIFEST
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 1d99dbf2fa4d..cc6d635459c5 100755
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5761,3 +5761,36 @@ pref("services.sync.engine.passwords.validation.maxRecords", 1000);
 // a sync.
 pref("services.sync.maxResyncs", 5);
 #endif // MOZ_SERVICES_SYNC
+
+// Marionette is the remote protocol that lets OOP programs communicate with,
+// instrument, and control Gecko.
+
+// Starts and stops the Marionette server.
+pref("marionette.enabled", false);
+
+// Delay server startup until a modal dialogue has been clicked to allow time
+// for user to set breakpoints in the Browser Toolbox.
+pref("marionette.debugging.clicktostart", false);
+
+// Verbosity of Marionette logger repository.
+//
+// Available levels are, in descending order of severity, "trace", "debug",
+// "config", "info", "warn", "error", and "fatal". The value is treated
+// case-insensitively.
+pref("marionette.log.level", "Info");
+
+// Certain log messages that are known to be long are truncated. This
+// preference causes them to not be truncated.
+pref("marionette.log.truncate", true);
+
+// Port to start Marionette server on.
+pref("marionette.port", 2828);
+
+// Sets recommended automation preferences when Marionette is started.
+pref("marionette.prefs.recommended", true);
+
+// Whether content scripts can be safely reused.
+//
+// Deprecated and scheduled for removal with
+// https://bugzil.la/marionette-window-tracking
+pref("marionette.contentListener", false);
diff --git a/testing/marionette/moz.build b/testing/marionette/moz.build
index 127b052454a0..c7d091102086 100644
--- a/testing/marionette/moz.build
+++ b/testing/marionette/moz.build
@@ -5,7 +5,6 @@
 DIRS += ["components"]
 
 JAR_MANIFESTS += ["jar.mn"]
-JS_PREFERENCE_FILES += ["prefs/marionette.js"]
 
 MARIONETTE_UNIT_MANIFESTS += ["harness/marionette_harness/tests/unit/unit-tests.ini"]
 XPCSHELL_TESTS_MANIFESTS += ["test/unit/xpcshell.ini"]
diff --git a/testing/marionette/prefs/marionette.js b/testing/marionette/prefs/marionette.js
deleted file mode 100644
index b423fa9dcfab..000000000000
--- a/testing/marionette/prefs/marionette.js
+++ /dev/null
@@ -1,38 +0,0 @@
-/* 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/. */
-
-/* global pref */
-
-// Marionette is the remote protocol that lets OOP programs
-// communicate with, instrument, and control Gecko.
-
-// Starts and stops the Marionette server.
-pref("marionette.enabled", false);
-
-// Delay server startup until a modal dialogue has been clicked to
-// allow time for user to set breakpoints in the Browser Toolbox.
-pref("marionette.debugging.clicktostart", false);
-
-// Verbosity of Marionette logger repository.
-//
-// Available levels are, in descending order of severity,
-// "trace", "debug", "config", "info", "warn", "error", and "fatal".
-// The value is treated case-insensitively.
-pref("marionette.log.level", "Info");
-
-// Certain log messages that are known to be long are truncated.
-// This preference causes them to not be truncated.
-pref("marionette.log.truncate", true);
-
-// Port to start Marionette server on.
-pref("marionette.port", 2828);
-
-// Sets recommended automation preferences when Marionette is started.
-pref("marionette.prefs.recommended", true);
-
-// Whether content scripts can be safely reused.
-//
-// Deprecated and scheduled for removal
-// with https://bugzil.la/marionette-window-tracking
-pref("marionette.contentListener", false);