diff --git a/testing/mozharness/mozharness/mozilla/testing/firefox_media_tests.py b/testing/mozharness/mozharness/mozilla/testing/firefox_media_tests.py
index 1ac393e95eff..dee4b0989c3f 100644
--- a/testing/mozharness/mozharness/mozilla/testing/firefox_media_tests.py
+++ b/testing/mozharness/mozharness/mozilla/testing/firefox_media_tests.py
@@ -84,6 +84,12 @@ media_test_config_options = [
       "default": False,
       "help": "Permits a software GL implementation (such as LLVMPipe) to use the GL compositor."
       }],
+    [["--enable-webrender"],
+     {"action": "store_true",
+      "dest": "enable_webrender",
+      "default": False,
+      "help": "Tries to enable the WebRender compositor."}
+      }],
 ] + (copy.deepcopy(testing_config_options))
 
 class JobResultParser(TestSummaryOutputParserHelper):
@@ -305,6 +311,8 @@ class FirefoxMediaTestsBase(TestingMixin, VCSToolsScript):
 
         if self.config['allow_software_gl_layers']:
             env['MOZ_LAYERS_ALLOW_SOFTWARE_GL'] = '1'
+        if self.config['enable_webrender']:
+            env['MOZ_WEBRENDER'] = '1'
 
         return_code = self.run_command(
             cmd,
diff --git a/testing/mozharness/mozharness/mozilla/testing/firefox_ui_tests.py b/testing/mozharness/mozharness/mozilla/testing/firefox_ui_tests.py
index 6b61ec0e3ae9..b05269d36562 100644
--- a/testing/mozharness/mozharness/mozilla/testing/firefox_ui_tests.py
+++ b/testing/mozharness/mozharness/mozilla/testing/firefox_ui_tests.py
@@ -32,6 +32,12 @@ firefox_ui_tests_config_options = [
         "default": False,
         "help": "Permits a software GL implementation (such as LLVMPipe) to use the GL compositor.",
     }],
+    [["--enable-webrender"], {
+        "action": "store_true",
+        "dest": "enable_webrender",
+        "default": False,
+        "help": "Tries to enable the WebRender compositor.",
+    }],
     [['--dry-run'], {
         'dest': 'dry_run',
         'default': False,
@@ -254,6 +260,8 @@ class FirefoxUITests(TestingMixin, VCSToolsScript, CodeCoverageMixin):
 
         if self.config['allow_software_gl_layers']:
             env['MOZ_LAYERS_ALLOW_SOFTWARE_GL'] = '1'
+        if self.config['enable_webrender']:
+            env['MOZ_WEBRENDER'] = '1'
 
         return_code = self.run_command(cmd,
                                        cwd=dirs['abs_work_dir'],
diff --git a/testing/mozharness/scripts/desktop_unittest.py b/testing/mozharness/scripts/desktop_unittest.py
index c08f8bdb5fc0..78405cd1e53a 100755
--- a/testing/mozharness/scripts/desktop_unittest.py
+++ b/testing/mozharness/scripts/desktop_unittest.py
@@ -156,6 +156,12 @@ class DesktopUnittest(TestingMixin, MercurialScript, BlobUploadMixin, MozbaseMix
             "default": False,
             "help": "Forcibly enable parallel traversal in Stylo with STYLO_THREADS=4"}
          ],
+        [["--enable-webrender"], {
+            "action": "store_true",
+            "dest": "enable_webrender",
+            "default": False,
+            "help": "Tries to enable the WebRender compositor."}
+         ],
     ] + copy.deepcopy(testing_config_options) + \
         copy.deepcopy(blobupload_config_options) + \
         copy.deepcopy(code_coverage_config_options)
@@ -710,6 +716,9 @@ class DesktopUnittest(TestingMixin, MercurialScript, BlobUploadMixin, MozbaseMix
 
                 if self.config['allow_software_gl_layers']:
                     env['MOZ_LAYERS_ALLOW_SOFTWARE_GL'] = '1'
+                if self.config['enable_webrender']:
+                    env['MOZ_WEBRENDER'] = '1'
+
                 env['STYLO_THREADS'] = '4' if self.config['parallel_stylo_traversal'] else '1'
 
                 env = self.query_env(partial_env=env, log_level=INFO)
diff --git a/testing/mozharness/scripts/marionette.py b/testing/mozharness/scripts/marionette.py
index 0b0c1cf6e07c..d0bb37654148 100755
--- a/testing/mozharness/scripts/marionette.py
+++ b/testing/mozharness/scripts/marionette.py
@@ -97,6 +97,13 @@ class MarionetteTest(TestingMixin, MercurialScript, BlobUploadMixin, TransferMix
         "default": False,
         "help": "Permits a software GL implementation (such as LLVMPipe) to use the GL compositor."
         }
+    ], [
+       ["--enable-webrender"],
+       {"action": "store_true",
+        "dest": "enable_webrender",
+        "default": False,
+        "help": "Tries to enable the WebRender compositor."
+        }
      ]] + copy.deepcopy(testing_config_options) \
         + copy.deepcopy(blobupload_config_options) \
         + copy.deepcopy(code_coverage_config_options)
@@ -311,6 +318,8 @@ class MarionetteTest(TestingMixin, MercurialScript, BlobUploadMixin, TransferMix
 
         if self.config['allow_software_gl_layers']:
             env['MOZ_LAYERS_ALLOW_SOFTWARE_GL'] = '1'
+        if self.config['enable_webrender']:
+            env['MOZ_WEBRENDER'] = '1'
 
         if not os.path.isdir(env['MOZ_UPLOAD_DIR']):
             self.mkdir_p(env['MOZ_UPLOAD_DIR'])
diff --git a/testing/mozharness/scripts/web_platform_tests.py b/testing/mozharness/scripts/web_platform_tests.py
index dd13b73b4856..5db640a4cb53 100755
--- a/testing/mozharness/scripts/web_platform_tests.py
+++ b/testing/mozharness/scripts/web_platform_tests.py
@@ -52,7 +52,14 @@ class WebPlatformTest(TestingMixin, MercurialScript, BlobUploadMixin, CodeCovera
             "action": "store_true",
             "dest": "allow_software_gl_layers",
             "default": False,
-            "help": "Permits a software GL implementation (such as LLVMPipe) to use the GL compositor."}]
+            "help": "Permits a software GL implementation (such as LLVMPipe) to use the GL compositor."}
+         ],
+        [["--enable-webrender"], {
+            "action": "store_true",
+            "dest": "enable_webrender",
+            "default": False,
+            "help": "Tries to enable the WebRender compositor."}
+         ]
     ] + copy.deepcopy(testing_config_options) + \
         copy.deepcopy(blobupload_config_options) + \
         copy.deepcopy(code_coverage_config_options)
@@ -245,6 +252,8 @@ class WebPlatformTest(TestingMixin, MercurialScript, BlobUploadMixin, CodeCovera
 
         if self.config['allow_software_gl_layers']:
             env['MOZ_LAYERS_ALLOW_SOFTWARE_GL'] = '1'
+        if self.config['enable_webrender']:
+            env['MOZ_WEBRENDER'] = '1'
 
         env = self.query_env(partial_env=env, log_level=INFO)