diff --git a/core/modules/block_content/block_content.routing.yml b/core/modules/block_content/block_content.routing.yml
index 35724a68b8f..65fc9e1df66 100644
--- a/core/modules/block_content/block_content.routing.yml
+++ b/core/modules/block_content/block_content.routing.yml
@@ -12,7 +12,7 @@ block_content.add_form:
   path: '/block/add/{block_content_type}'
   defaults:
     _controller: '\Drupal\block_content\Controller\BlockContentController::addForm'
-    _title_callback: 'Drupal\block_content\Controller\BlockContentController::getAddFormTitle'
+    _title_callback: '\Drupal\block_content\Controller\BlockContentController::getAddFormTitle'
   options:
     _admin_route: TRUE
   requirements:
diff --git a/core/modules/book/book.routing.yml b/core/modules/book/book.routing.yml
index 772a6cf391a..0a4b783a7c9 100644
--- a/core/modules/book/book.routing.yml
+++ b/core/modules/book/book.routing.yml
@@ -46,7 +46,7 @@ entity.node.book_outline_form:
 book.admin_edit:
   path: '/admin/structure/book/{node}'
   defaults:
-    _form: 'Drupal\book\Form\BookAdminEditForm'
+    _form: '\Drupal\book\Form\BookAdminEditForm'
     _title: 'Re-order book pages and change titles'
   requirements:
     _permission: 'administer book outlines'
diff --git a/core/modules/comment/comment.routing.yml b/core/modules/comment/comment.routing.yml
index 6daeace36a8..e92e8daf797 100644
--- a/core/modules/comment/comment.routing.yml
+++ b/core/modules/comment/comment.routing.yml
@@ -95,7 +95,7 @@ comment.new_comments_node_links:
 comment.node_redirect:
   path: '/comment/{node}/reply'
   defaults:
-    _controller: 'Drupal\comment\Controller\CommentController::redirectNode'
+    _controller: '\Drupal\comment\Controller\CommentController::redirectNode'
   requirements:
     _entity_access: 'node.view'
     _module_dependencies: 'node'
diff --git a/core/modules/file/tests/file_test/file_test.routing.yml b/core/modules/file/tests/file_test/file_test.routing.yml
index 1c5a7632e66..0505615a4e5 100644
--- a/core/modules/file/tests/file_test/file_test.routing.yml
+++ b/core/modules/file/tests/file_test/file_test.routing.yml
@@ -1,12 +1,12 @@
 file.test:
   path: '/file-test/upload'
   defaults:
-    _form: 'Drupal\file_test\Form\FileTestForm'
+    _form: '\Drupal\file_test\Form\FileTestForm'
   requirements:
     _access: 'TRUE'
 file.save_upload_from_form_test:
   path: '/file-test/save_upload_from_form_test'
   defaults:
-    _form: 'Drupal\file_test\Form\FileTestSaveUploadFromForm'
+    _form: '\Drupal\file_test\Form\FileTestSaveUploadFromForm'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/filter/tests/filter_test/filter_test.routing.yml b/core/modules/filter/tests/filter_test/filter_test.routing.yml
index 14bb7ab15a1..1144c2bd845 100644
--- a/core/modules/filter/tests/filter_test/filter_test.routing.yml
+++ b/core/modules/filter/tests/filter_test/filter_test.routing.yml
@@ -3,6 +3,6 @@ filter_text.text_format:
   path: '/filter-test/text-format'
   defaults:
     _title: 'Text format test forms'
-    _form: 'Drupal\filter_test\Form\FilterTestFormatForm'
+    _form: '\Drupal\filter_test\Form\FilterTestFormatForm'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/jsonapi/jsonapi.routing.yml b/core/modules/jsonapi/jsonapi.routing.yml
index e5bcaf72dbb..02b908a3538 100644
--- a/core/modules/jsonapi/jsonapi.routing.yml
+++ b/core/modules/jsonapi/jsonapi.routing.yml
@@ -4,7 +4,7 @@ route_callbacks:
 jsonapi.settings:
   path: '/admin/config/services/jsonapi'
   defaults:
-    _form: 'Drupal\jsonapi\Form\JsonApiSettingsForm'
+    _form: '\Drupal\jsonapi\Form\JsonApiSettingsForm'
     _title: 'JSON:API'
   requirements:
     _permission: 'administer site configuration'
diff --git a/core/modules/language/language.routing.yml b/core/modules/language/language.routing.yml
index 84740ee0668..ffe4b5be4b4 100644
--- a/core/modules/language/language.routing.yml
+++ b/core/modules/language/language.routing.yml
@@ -1,7 +1,7 @@
 language.negotiation_url:
   path: '/admin/config/regional/language/detection/url'
   defaults:
-    _form: 'Drupal\language\Form\NegotiationUrlForm'
+    _form: '\Drupal\language\Form\NegotiationUrlForm'
     _title: 'URL language detection configuration'
   requirements:
     _permission: 'administer languages'
@@ -9,7 +9,7 @@ language.negotiation_url:
 language.negotiation_session:
   path: '/admin/config/regional/language/detection/session'
   defaults:
-    _form: 'Drupal\language\Form\NegotiationSessionForm'
+    _form: '\Drupal\language\Form\NegotiationSessionForm'
     _title: 'Session language detection configuration'
   requirements:
     _permission: 'administer languages'
@@ -17,7 +17,7 @@ language.negotiation_session:
 language.negotiation_selected:
   path: '/admin/config/regional/language/detection/selected'
   defaults:
-    _form: 'Drupal\language\Form\NegotiationSelectedForm'
+    _form: '\Drupal\language\Form\NegotiationSelectedForm'
     _title: 'Selected language configuration'
   requirements:
     _permission: 'administer languages'
@@ -82,6 +82,6 @@ language.content_settings_page:
   path: '/admin/config/regional/content-language'
   defaults:
     _title: 'Content language'
-    _form: 'Drupal\language\Form\ContentLanguageSettingsForm'
+    _form: '\Drupal\language\Form\ContentLanguageSettingsForm'
   requirements:
     _permission: 'administer languages'
diff --git a/core/modules/locale/locale.routing.yml b/core/modules/locale/locale.routing.yml
index 593e1ff672a..9f59d07307c 100644
--- a/core/modules/locale/locale.routing.yml
+++ b/core/modules/locale/locale.routing.yml
@@ -1,7 +1,7 @@
 locale.settings:
   path: '/admin/config/regional/translate/settings'
   defaults:
-    _form: 'Drupal\locale\Form\LocaleSettingsForm'
+    _form: '\Drupal\locale\Form\LocaleSettingsForm'
     _title: 'Interface translation settings'
   requirements:
     _permission: 'translate interface'
@@ -9,7 +9,7 @@ locale.settings:
 locale.check_translation:
   path: '/admin/reports/translations/check'
   defaults:
-    _controller: 'Drupal\locale\Controller\LocaleController::checkTranslation'
+    _controller: '\Drupal\locale\Controller\LocaleController::checkTranslation'
   requirements:
     _permission: 'translate interface'
 
diff --git a/core/modules/menu_ui/menu_ui.routing.yml b/core/modules/menu_ui/menu_ui.routing.yml
index 7f94a6d7157..39c917209c5 100644
--- a/core/modules/menu_ui/menu_ui.routing.yml
+++ b/core/modules/menu_ui/menu_ui.routing.yml
@@ -16,7 +16,7 @@ menu_ui.parent_options_js:
 menu_ui.link_edit:
   path: '/admin/structure/menu/link/{menu_link_plugin}/edit'
   defaults:
-    _form: 'Drupal\menu_ui\Form\MenuLinkEditForm'
+    _form: '\Drupal\menu_ui\Form\MenuLinkEditForm'
     _title: 'Edit menu link'
   options:
     parameters:
@@ -28,7 +28,7 @@ menu_ui.link_edit:
 menu_ui.link_reset:
   path: '/admin/structure/menu/link/{menu_link_plugin}/reset'
   defaults:
-    _form: 'Drupal\menu_ui\Form\MenuLinkResetForm'
+    _form: '\Drupal\menu_ui\Form\MenuLinkResetForm'
     _title: 'Reset menu link'
   options:
     parameters:
diff --git a/core/modules/node/node.routing.yml b/core/modules/node/node.routing.yml
index d592bd1a1b1..86951777fc4 100644
--- a/core/modules/node/node.routing.yml
+++ b/core/modules/node/node.routing.yml
@@ -137,6 +137,6 @@ entity.node_type.delete_form:
 node.configure_rebuild_confirm:
   path: '/admin/reports/status/rebuild'
   defaults:
-    _form: 'Drupal\node\Form\RebuildPermissionsForm'
+    _form: '\Drupal\node\Form\RebuildPermissionsForm'
   requirements:
     _permission: 'access administration pages'
diff --git a/core/modules/shortcut/shortcut.routing.yml b/core/modules/shortcut/shortcut.routing.yml
index 11333575690..0bf0a3bd281 100644
--- a/core/modules/shortcut/shortcut.routing.yml
+++ b/core/modules/shortcut/shortcut.routing.yml
@@ -33,7 +33,7 @@ entity.shortcut_set.edit_form:
 shortcut.link_add_inline:
   path: '/admin/config/user-interface/shortcut/manage/{shortcut_set}/add-link-inline'
   defaults:
-    _controller: 'Drupal\shortcut\Controller\ShortcutSetController::addShortcutLinkInline'
+    _controller: '\Drupal\shortcut\Controller\ShortcutSetController::addShortcutLinkInline'
   requirements:
     _entity_access: 'shortcut_set.update'
     _csrf_token: 'TRUE'
@@ -75,7 +75,7 @@ entity.shortcut.edit_form:
 entity.shortcut.link_delete_inline:
   path: '/admin/config/user-interface/shortcut/link/{shortcut}/delete-inline'
   defaults:
-    _controller: 'Drupal\shortcut\Controller\ShortcutController::deleteShortcutLinkInline'
+    _controller: '\Drupal\shortcut\Controller\ShortcutController::deleteShortcutLinkInline'
   requirements:
     _entity_access: 'shortcut.delete'
     _csrf_token: 'TRUE'
@@ -93,10 +93,10 @@ entity.shortcut.delete_form:
 shortcut.set_switch:
   path: '/user/{user}/shortcuts'
   defaults:
-    _form: 'Drupal\shortcut\Form\SwitchShortcutSet'
+    _form: '\Drupal\shortcut\Form\SwitchShortcutSet'
     _title: 'Shortcuts'
   requirements:
-    _custom_access: 'Drupal\shortcut\Form\SwitchShortcutSet::checkAccess'
+    _custom_access: '\Drupal\shortcut\Form\SwitchShortcutSet::checkAccess'
   options:
     _admin_route: TRUE
     user: \d+
diff --git a/core/modules/simpletest/simpletest.routing.yml b/core/modules/simpletest/simpletest.routing.yml
index 43016b20e95..b4e81e7a496 100644
--- a/core/modules/simpletest/simpletest.routing.yml
+++ b/core/modules/simpletest/simpletest.routing.yml
@@ -1,7 +1,7 @@
 simpletest.settings:
   path: '/admin/config/development/testing/settings'
   defaults:
-    _form: 'Drupal\simpletest\Form\SimpletestSettingsForm'
+    _form: '\Drupal\simpletest\Form\SimpletestSettingsForm'
     _title: 'Test settings'
   requirements:
     _permission: 'administer unit tests'
@@ -17,7 +17,7 @@ simpletest.test_form:
 simpletest.result_form:
   path: '/admin/config/development/testing/results/{test_id}'
   defaults:
-    _form: 'Drupal\simpletest\Form\SimpletestResultsForm'
+    _form: '\Drupal\simpletest\Form\SimpletestResultsForm'
     _title: 'Test result'
   requirements:
     _permission: 'administer unit tests'
diff --git a/core/modules/statistics/statistics.routing.yml b/core/modules/statistics/statistics.routing.yml
index d5ea04c3f2c..6edf4ca8913 100644
--- a/core/modules/statistics/statistics.routing.yml
+++ b/core/modules/statistics/statistics.routing.yml
@@ -1,7 +1,7 @@
 statistics.settings:
   path: '/admin/config/system/statistics'
   defaults:
-    _form: 'Drupal\statistics\StatisticsSettingsForm'
+    _form: '\Drupal\statistics\StatisticsSettingsForm'
     _title: 'Statistics'
   requirements:
     _permission: 'administer statistics'
diff --git a/core/modules/system/system.routing.yml b/core/modules/system/system.routing.yml
index 9cfe2ca54c2..9591d84d690 100644
--- a/core/modules/system/system.routing.yml
+++ b/core/modules/system/system.routing.yml
@@ -138,7 +138,7 @@ system.cron:
 system.admin_compact_page:
   path: '/admin/compact/{mode}'
   defaults:
-    _controller: 'Drupal\system\Controller\SystemController::compactPage'
+    _controller: '\Drupal\system\Controller\SystemController::compactPage'
     mode: 'off'
   requirements:
     _permission: 'access administration pages'
@@ -153,7 +153,7 @@ system.machine_name_transliterate:
 system.site_information_settings:
   path: '/admin/config/system/site-information'
   defaults:
-    _form: 'Drupal\system\Form\SiteInformationForm'
+    _form: '\Drupal\system\Form\SiteInformationForm'
     _title: 'Basic site settings'
   requirements:
     _permission: 'administer site configuration'
@@ -161,7 +161,7 @@ system.site_information_settings:
 system.cron_settings:
   path: '/admin/config/system/cron'
   defaults:
-    _form: 'Drupal\system\Form\CronForm'
+    _form: '\Drupal\system\Form\CronForm'
     _title: 'Cron'
   requirements:
     _permission: 'administer site configuration'
@@ -169,7 +169,7 @@ system.cron_settings:
 system.logging_settings:
   path: '/admin/config/development/logging'
   defaults:
-    _form: 'Drupal\system\Form\LoggingForm'
+    _form: '\Drupal\system\Form\LoggingForm'
     _title: 'Logging and errors'
   requirements:
     _permission: 'administer site configuration'
@@ -177,7 +177,7 @@ system.logging_settings:
 system.performance_settings:
   path: '/admin/config/development/performance'
   defaults:
-    _form: 'Drupal\system\Form\PerformanceForm'
+    _form: '\Drupal\system\Form\PerformanceForm'
     _title: 'Performance'
   requirements:
     _permission: 'administer site configuration'
@@ -185,7 +185,7 @@ system.performance_settings:
 system.file_system_settings:
   path: '/admin/config/media/file-system'
   defaults:
-    _form: 'Drupal\system\Form\FileSystemForm'
+    _form: '\Drupal\system\Form\FileSystemForm'
     _title: 'File system'
   requirements:
     _permission: 'administer site configuration'
@@ -193,7 +193,7 @@ system.file_system_settings:
 system.rss_feeds_settings:
   path: '/admin/config/services/rss-publishing'
   defaults:
-    _form: 'Drupal\system\Form\RssFeedsForm'
+    _form: '\Drupal\system\Form\RssFeedsForm'
     _title: 'RSS publishing'
   requirements:
     _permission: 'administer site configuration'
@@ -201,7 +201,7 @@ system.rss_feeds_settings:
 system.regional_settings:
   path: '/admin/config/regional/settings'
   defaults:
-    _form: 'Drupal\system\Form\RegionalForm'
+    _form: '\Drupal\system\Form\RegionalForm'
     _title: 'Regional settings'
   requirements:
     _permission: 'administer site configuration'
@@ -209,7 +209,7 @@ system.regional_settings:
 system.image_toolkit_settings:
   path: '/admin/config/media/image-toolkit'
   defaults:
-    _form: 'Drupal\system\Form\ImageToolkitForm'
+    _form: '\Drupal\system\Form\ImageToolkitForm'
     _title: 'Image toolkit'
   requirements:
     _permission: 'administer site configuration'
@@ -217,7 +217,7 @@ system.image_toolkit_settings:
 system.site_maintenance_mode:
   path: '/admin/config/development/maintenance'
   defaults:
-    _form: 'Drupal\system\Form\SiteMaintenanceModeForm'
+    _form: '\Drupal\system\Form\SiteMaintenanceModeForm'
     _title: 'Maintenance mode'
   requirements:
     _permission: 'administer site configuration'
@@ -269,14 +269,14 @@ system.modules_list:
   defaults:
     _title: 'Extend'
     _title_context: 'With components'
-    _form: 'Drupal\system\Form\ModulesListForm'
+    _form: '\Drupal\system\Form\ModulesListForm'
   requirements:
     _permission: 'administer modules'
 
 system.modules_list_confirm:
   path: '/admin/modules/list/confirm'
   defaults:
-    _form: 'Drupal\system\Form\ModulesListConfirmForm'
+    _form: '\Drupal\system\Form\ModulesListConfirmForm'
     _title: 'Some required modules must be enabled'
   requirements:
     _permission: 'administer modules'
@@ -284,7 +284,7 @@ system.modules_list_confirm:
 system.modules_list_experimental_confirm:
   path: '/admin/modules/list/confirm-experimental'
   defaults:
-    _form: 'Drupal\system\Form\ModulesListExperimentalConfirmForm'
+    _form: '\Drupal\system\Form\ModulesListExperimentalConfirmForm'
     _title: 'Experimental modules'
   requirements:
     _permission: 'administer modules'
@@ -292,7 +292,7 @@ system.modules_list_experimental_confirm:
 system.theme_uninstall:
   path: '/admin/appearance/uninstall'
   defaults:
-    _controller: 'Drupal\system\Controller\ThemeController::uninstall'
+    _controller: '\Drupal\system\Controller\ThemeController::uninstall'
   requirements:
     _permission: 'administer themes'
     _csrf_token: 'TRUE'
@@ -300,7 +300,7 @@ system.theme_uninstall:
 system.theme_install:
   path: '/admin/appearance/install'
   defaults:
-    _controller: 'Drupal\system\Controller\ThemeController::install'
+    _controller: '\Drupal\system\Controller\ThemeController::install'
   requirements:
     _permission: 'administer themes'
     _csrf_token: 'TRUE'
@@ -316,7 +316,7 @@ system.status:
 system.php:
   path: '/admin/reports/status/php'
   defaults:
-    _controller: 'Drupal\system\Controller\SystemInfoController::php'
+    _controller: '\Drupal\system\Controller\SystemInfoController::php'
   requirements:
     _permission: 'administer site configuration'
   # This page should not be treated as administrative since it outputs its own
@@ -335,7 +335,7 @@ system.admin_index:
 system.files:
   path: '/system/files/{scheme}'
   defaults:
-    _controller: 'Drupal\system\FileDownloadController::download'
+    _controller: '\Drupal\system\FileDownloadController::download'
     scheme: private
   requirements:
     _access: 'TRUE'
@@ -343,7 +343,7 @@ system.files:
 system.private_file_download:
   path: '/system/files/{filepath}'
   defaults:
-    _controller: 'Drupal\system\FileDownloadController::download'
+    _controller: '\Drupal\system\FileDownloadController::download'
   requirements:
     # Permissive regex to allow slashes in filepath see
     # http://symfony.com/doc/current/cookbook/routing/slash_in_parameter.html
@@ -418,7 +418,7 @@ system.theme_settings_theme:
 system.modules_uninstall:
   path: '/admin/modules/uninstall'
   defaults:
-    _form: 'Drupal\system\Form\ModulesUninstallForm'
+    _form: '\Drupal\system\Form\ModulesUninstallForm'
     _title: 'Uninstall'
   requirements:
     _permission: 'administer modules'
@@ -426,7 +426,7 @@ system.modules_uninstall:
 system.modules_uninstall_confirm:
   path: '/admin/modules/uninstall/confirm'
   defaults:
-    _form: 'Drupal\system\Form\ModulesUninstallConfirmForm'
+    _form: '\Drupal\system\Form\ModulesUninstallConfirmForm'
     _title: 'Confirm uninstall'
   requirements:
     _permission: 'administer modules'
diff --git a/core/modules/system/tests/modules/js_webassert_test/js_webassert_test.routing.yml b/core/modules/system/tests/modules/js_webassert_test/js_webassert_test.routing.yml
index 2be8984a91d..5d2678949cc 100644
--- a/core/modules/system/tests/modules/js_webassert_test/js_webassert_test.routing.yml
+++ b/core/modules/system/tests/modules/js_webassert_test/js_webassert_test.routing.yml
@@ -1,7 +1,7 @@
 js_webassert_test.js_webassert_test_form:
   path: '/js_webassert_test_form'
   defaults:
-    _form: 'Drupal\js_webassert_test\Form\JsWebAssertTestForm'
+    _form: '\Drupal\js_webassert_test\Form\JsWebAssertTestForm'
     _title: 'JsWebAssertForm'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/system/tests/modules/router_test_directory/router_test.routing.yml b/core/modules/system/tests/modules/router_test_directory/router_test.routing.yml
index 4d5d241baaa..2006738d611 100644
--- a/core/modules/system/tests/modules/router_test_directory/router_test.routing.yml
+++ b/core/modules/system/tests/modules/router_test_directory/router_test.routing.yml
@@ -165,7 +165,7 @@ router_test.25:
 router_test.26:
   path: '/router_test/test26'
   defaults:
-    _form: 'Drupal\system\Form\LoggingForm'
+    _form: '\Drupal\system\Form\LoggingForm'
     _title: 'Cron'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml b/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml
index 8579b78d063..08fa101b7c9 100644
--- a/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml
+++ b/core/modules/system/tests/modules/test_page_test/test_page_test.routing.yml
@@ -32,7 +32,7 @@ test_page_test.dynamic_title:
   path: '/test-page-dynamic-title'
   defaults:
     _controller: '\Drupal\test_page_test\Controller\Test::staticTitle'
-    _title_callback: 'Drupal\test_page_test\Controller\Test::dynamicTitle'
+    _title_callback: '\Drupal\test_page_test\Controller\Test::dynamicTitle'
   requirements:
     _access: 'TRUE'
 
diff --git a/core/modules/system/tests/modules/trusted_hosts_test/trusted_hosts_test.routing.yml b/core/modules/system/tests/modules/trusted_hosts_test/trusted_hosts_test.routing.yml
index 834aeace01e..607710873c9 100644
--- a/core/modules/system/tests/modules/trusted_hosts_test/trusted_hosts_test.routing.yml
+++ b/core/modules/system/tests/modules/trusted_hosts_test/trusted_hosts_test.routing.yml
@@ -1,6 +1,6 @@
 trusted_hosts_test.fake_request:
   path: '/trusted-hosts-test/fake-request'
   defaults:
-    _controller: 'Drupal\trusted_hosts_test\Controller\TrustedHostsTestController::fakeRequestHost'
+    _controller: '\Drupal\trusted_hosts_test\Controller\TrustedHostsTestController::fakeRequestHost'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/taxonomy/tests/modules/vocabulary_serialization_test/vocabulary_serialization_test.routing.yml b/core/modules/taxonomy/tests/modules/vocabulary_serialization_test/vocabulary_serialization_test.routing.yml
index 82f2b2222cf..c7ed617405f 100644
--- a/core/modules/taxonomy/tests/modules/vocabulary_serialization_test/vocabulary_serialization_test.routing.yml
+++ b/core/modules/taxonomy/tests/modules/vocabulary_serialization_test/vocabulary_serialization_test.routing.yml
@@ -1,6 +1,6 @@
 vocabulary_serialization_test:
   path: '/vocabulary_serialization_test/{taxonomy_vocabulary}'
   defaults:
-    _controller: 'Drupal\vocabulary_serialization_test\VocabularySerializationTestController::vocabularyResponse'
+    _controller: '\Drupal\vocabulary_serialization_test\VocabularySerializationTestController::vocabularyResponse'
   requirements:
     _access: 'TRUE'
diff --git a/core/modules/update/tests/modules/update_test/update_test.routing.yml b/core/modules/update/tests/modules/update_test/update_test.routing.yml
index 5dd8d4c745e..395a54d2710 100644
--- a/core/modules/update/tests/modules/update_test/update_test.routing.yml
+++ b/core/modules/update/tests/modules/update_test/update_test.routing.yml
@@ -1,7 +1,7 @@
 update_test.503:
   path: '/503-error'
   defaults:
-    _controller: 'Drupal\update_test\Controller\UpdateTestController::updateError'
+    _controller: '\Drupal\update_test\Controller\UpdateTestController::updateError'
   requirements:
     _access: 'TRUE'