diff --git a/core/modules/block/tests/src/Kernel/Migrate/d7/MigrateBlockContentTranslationTest.php b/core/modules/block/tests/src/Kernel/Migrate/d7/MigrateBlockContentTranslationTest.php
index 059cc1ba9f4bfe89984da78b3168508c4d4ded15..6c346aeac4f01f47ad93c38516b02c3490e75249 100644
--- a/core/modules/block/tests/src/Kernel/Migrate/d7/MigrateBlockContentTranslationTest.php
+++ b/core/modules/block/tests/src/Kernel/Migrate/d7/MigrateBlockContentTranslationTest.php
@@ -8,6 +8,7 @@
  * Tests migration of i18n block translations.
  *
  * @group migrate_drupal_7
+ * @group #slow
  */
 class MigrateBlockContentTranslationTest extends MigrateDrupal7TestBase {
 
diff --git a/core/modules/book/tests/src/Functional/BookTest.php b/core/modules/book/tests/src/Functional/BookTest.php
index 63a73cbec3fd14b31b28ee8769ca24d6849019eb..ffbc1ec1b41e33c62d95c5b6a6e67fdf0da7e046 100644
--- a/core/modules/book/tests/src/Functional/BookTest.php
+++ b/core/modules/book/tests/src/Functional/BookTest.php
@@ -10,6 +10,7 @@
  * Create a book, add pages, and test book interface.
  *
  * @group book
+ * @group #slow
  */
 class BookTest extends BrowserTestBase {
 
diff --git a/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageTest.php b/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageTest.php
index 2701e48dd957e78d9ba4da0fa2d63c06298d41b7..3726b682743432ff495cab7a856c4e23d315fd7c 100644
--- a/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageTest.php
+++ b/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageTest.php
@@ -13,6 +13,7 @@
 /**
  * @coversDefaultClass \Drupal\ckeditor5\Plugin\CKEditor5Plugin\Image
  * @group ckeditor5
+ * @group #slow
  * @internal
  */
 class ImageTest extends ImageTestBase {
diff --git a/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageUrlTest.php b/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageUrlTest.php
index 6b0e38fc96024cbce66dd7d0ef393c3fa128568b..7e363064d24e01ef63dda4649dee5b3fe84b3be2 100644
--- a/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageUrlTest.php
+++ b/core/modules/ckeditor5/tests/src/FunctionalJavascript/ImageUrlTest.php
@@ -12,6 +12,7 @@
 /**
  * @coversDefaultClass \Drupal\ckeditor5\Plugin\CKEditor5Plugin\Image
  * @group ckeditor5
+ * @group #slow
  * @internal
  */
 class ImageUrlTest extends ImageTestBase {
diff --git a/core/modules/ckeditor5/tests/src/FunctionalJavascript/MediaTest.php b/core/modules/ckeditor5/tests/src/FunctionalJavascript/MediaTest.php
index ece97daa4619049141bf1f45c8b3aed470ce377f..52e03e291f0c7b68692a9388f743dd805daaa314 100644
--- a/core/modules/ckeditor5/tests/src/FunctionalJavascript/MediaTest.php
+++ b/core/modules/ckeditor5/tests/src/FunctionalJavascript/MediaTest.php
@@ -26,6 +26,7 @@
 /**
  * @coversDefaultClass \Drupal\ckeditor5\Plugin\CKEditor5Plugin\Media
  * @group ckeditor5
+ * @group #slow
  * @internal
  */
 class MediaTest extends WebDriverTestBase {
diff --git a/core/modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php b/core/modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php
index 14f47c9a0c3e10e2ee448b30db15cbafd8808faa..f655343a083dd12d75526e293a5a625c41fdac36 100644
--- a/core/modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php
+++ b/core/modules/ckeditor5/tests/src/FunctionalJavascript/SourceEditingTest.php
@@ -15,6 +15,7 @@
  * @coversDefaultClass \Drupal\ckeditor5\Plugin\CKEditor5Plugin\SourceEditing
  * @covers \Drupal\ckeditor5\Plugin\CKEditor5PluginManager::getCKEditor5PluginConfig
  * @group ckeditor5
+ * @group #slow
  * @internal
  */
 class SourceEditingTest extends CKEditor5TestBase {
diff --git a/core/modules/config/tests/src/Functional/ConfigImportAllTest.php b/core/modules/config/tests/src/Functional/ConfigImportAllTest.php
index 10e6d4710140039228c89e2a7d64d1344824bc36..4d693c633378596bbcb674aefbb3afffa8b64723 100644
--- a/core/modules/config/tests/src/Functional/ConfigImportAllTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigImportAllTest.php
@@ -15,6 +15,7 @@
  * of all default configuration is also tested.
  *
  * @group config
+ * @group #slow
  */
 class ConfigImportAllTest extends ModuleTestBase {
 
diff --git a/core/modules/config/tests/src/Functional/ConfigImportUITest.php b/core/modules/config/tests/src/Functional/ConfigImportUITest.php
index bfb329686835b2148aeb6f251e2897b7c60cc7d6..35946054d232bff7381aeb7de6f3b050bbd0b340 100644
--- a/core/modules/config/tests/src/Functional/ConfigImportUITest.php
+++ b/core/modules/config/tests/src/Functional/ConfigImportUITest.php
@@ -10,6 +10,7 @@
  * Tests the user interface for importing configuration.
  *
  * @group config
+ * @group #slow
  */
 class ConfigImportUITest extends BrowserTestBase {
 
diff --git a/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php b/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php
index 314c3d50dbb4a3083b1e3e881bd8301264bb4010..f7035ec7a6a34efa9381e6f33edb2a50971aab89 100644
--- a/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php
@@ -17,6 +17,7 @@
  * and uninstall functionality is tested.
  *
  * @group config
+ * @group #slow
  */
 class ConfigInstallWebTest extends BrowserTestBase {
 
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php
index 688009de5bbe1cc978080497412e6f0f888266ad..f3e5e4585f98d512e1bc19d1614118b4cee9d0b1 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php
@@ -19,6 +19,7 @@
  * Translate settings and entities to various languages.
  *
  * @group config_translation
+ * @group #slow
  */
 class ConfigTranslationUiTest extends BrowserTestBase {
 
diff --git a/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php b/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php
index b92be50c5e0b07b3d1bf7f83e493e63bb4823e94..6589ec00f199821a3540aaca3a408bbe449bdc95 100644
--- a/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php
+++ b/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php
@@ -17,6 +17,7 @@
  *
  * @group content_moderation
  * @group workspaces
+ * @group #slow
  */
 class WorkspacesContentModerationStateTest extends ContentModerationStateTest {
 
diff --git a/core/modules/field/tests/src/Functional/FormTest.php b/core/modules/field/tests/src/Functional/FormTest.php
index cc94de8cdf88c4b6c911433dc893ea081c59ce2a..45eddc53cf0e00ac3d327a2fc2c290f38d5dae77 100644
--- a/core/modules/field/tests/src/Functional/FormTest.php
+++ b/core/modules/field/tests/src/Functional/FormTest.php
@@ -15,6 +15,7 @@
  * Tests field form handling.
  *
  * @group field
+ * @group #slow
  */
 class FormTest extends FieldTestBase {
 
diff --git a/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php b/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
index f6813227137ada0d3a3800bbbe8da6f1c22baca4..38c6c43076a7075efc9e7136ae9447d36ff88a26 100644
--- a/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
+++ b/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
@@ -21,6 +21,7 @@
  * Tests the Field UI "Manage fields" screen.
  *
  * @group field_ui
+ * @group #slow
  */
 class ManageFieldsFunctionalTest extends BrowserTestBase {
 
diff --git a/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php b/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php
index 2df9ae0b2af4fff5943e7f27a647e5fdbabce2b6..a0d689169c12e3d880429c97d4370209b8bffede 100644
--- a/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php
@@ -12,6 +12,7 @@
  * JSON:API integration test for the "BlockContent" content entity type.
  *
  * @group jsonapi
+ * @group #slow
  */
 class BlockContentTest extends ResourceTestBase {
 
diff --git a/core/modules/jsonapi/tests/src/Functional/CommentTest.php b/core/modules/jsonapi/tests/src/Functional/CommentTest.php
index ffc4db25356c0899ced2d6dbf77d4aca0d17072c..a291e53982574ebdeff6d0e0867c104cade7f74f 100644
--- a/core/modules/jsonapi/tests/src/Functional/CommentTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/CommentTest.php
@@ -21,6 +21,7 @@
  * JSON:API integration test for the "Comment" content entity type.
  *
  * @group jsonapi
+ * @group #slow
  */
 class CommentTest extends ResourceTestBase {
 
diff --git a/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php b/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php
index b054b694b23fbcc066d4086ad4db089740630eeb..0d23e93d4b02e00fd1577f3c86d223897b7e7c70 100644
--- a/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php
@@ -20,6 +20,7 @@
  * Tests binary data file upload route.
  *
  * @group jsonapi
+ * @group #slow
  */
 class FileUploadTest extends ResourceTestBase {
 
diff --git a/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php b/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php
index dcd442f553615c8939a8b0b6fc32dd4bc85817dc..c084bc6e31616d744f6f8f1143faaa3be200725b 100644
--- a/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php
@@ -31,6 +31,7 @@
  * JSON:API regression tests.
  *
  * @group jsonapi
+ * @group #slow
  *
  * @internal
  */
diff --git a/core/modules/jsonapi/tests/src/Functional/UserTest.php b/core/modules/jsonapi/tests/src/Functional/UserTest.php
index f1b68d225309f4db345a2862be34d854183fb0ac..56090392619ea15f13dd468fd5e33fe6b6188c3f 100644
--- a/core/modules/jsonapi/tests/src/Functional/UserTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/UserTest.php
@@ -17,6 +17,7 @@
  * JSON:API integration test for the "User" content entity type.
  *
  * @group jsonapi
+ * @group #slow
  */
 class UserTest extends ResourceTestBase {
 
diff --git a/core/modules/jsonapi/tests/src/Kernel/Context/FieldResolverTest.php b/core/modules/jsonapi/tests/src/Kernel/Context/FieldResolverTest.php
index b15896dc4ab277a0a175914fc27d9f82b85d1d49..f53992897980827a7eb98cb9ef53c2b691e85757 100644
--- a/core/modules/jsonapi/tests/src/Kernel/Context/FieldResolverTest.php
+++ b/core/modules/jsonapi/tests/src/Kernel/Context/FieldResolverTest.php
@@ -11,6 +11,7 @@
 /**
  * @coversDefaultClass \Drupal\jsonapi\Context\FieldResolver
  * @group jsonapi
+ * @group #slow
  *
  * @internal
  */
diff --git a/core/modules/language/tests/src/Kernel/ContentLanguageSettingsValidationTest.php b/core/modules/language/tests/src/Kernel/ContentLanguageSettingsValidationTest.php
index 07bab877aafb9005a72a496f43727e6a2c691f0a..ba245ad0b594b175c474c45a981c062ce015dfbc 100644
--- a/core/modules/language/tests/src/Kernel/ContentLanguageSettingsValidationTest.php
+++ b/core/modules/language/tests/src/Kernel/ContentLanguageSettingsValidationTest.php
@@ -9,6 +9,7 @@
  * Tests validation of content_language_settings entities.
  *
  * @group language
+ * @group #slow
  */
 class ContentLanguageSettingsValidationTest extends ConfigEntityValidationTestBase {
 
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
index 296ab0c4a7c9a2cce5f4775fed15a51a4fa181ab..1eebaa4663e49d12b8aee541a0f6b971b1c504f6 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
@@ -13,6 +13,7 @@
  * Tests the Layout Builder UI.
  *
  * @group layout_builder
+ * @group #slow
  */
 class LayoutBuilderTest extends BrowserTestBase {
 
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php
index 976a38b3a40fece62b4785b5912cdff73a550a60..e635a84863a543dc986c2ccee305a881e31149de 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php
@@ -9,6 +9,7 @@
  * Tests that the inline block feature works correctly.
  *
  * @group layout_builder
+ * @group #slow
  */
 class InlineBlockTest extends InlineBlockTestBase {
 
diff --git a/core/modules/layout_builder/tests/src/Kernel/LayoutBuilderEntityViewDisplayTest.php b/core/modules/layout_builder/tests/src/Kernel/LayoutBuilderEntityViewDisplayTest.php
index 53f61b49e32eb99758ffd362e511f02fb0dc5e42..e0df4ad034bc51334e55d92a5ba81f5354b7beef 100644
--- a/core/modules/layout_builder/tests/src/Kernel/LayoutBuilderEntityViewDisplayTest.php
+++ b/core/modules/layout_builder/tests/src/Kernel/LayoutBuilderEntityViewDisplayTest.php
@@ -9,6 +9,7 @@
  * @coversDefaultClass \Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay
  *
  * @group layout_builder
+ * @group #slow
  */
 class LayoutBuilderEntityViewDisplayTest extends SectionListTestBase {
 
diff --git a/core/modules/layout_builder/tests/src/Kernel/OverridesSectionStorageTest.php b/core/modules/layout_builder/tests/src/Kernel/OverridesSectionStorageTest.php
index f247117b26ee37588450bfe0c0fa17c6959b4963..b4dbf785e17dbaff53894dfa396c43a4abeee3bb 100644
--- a/core/modules/layout_builder/tests/src/Kernel/OverridesSectionStorageTest.php
+++ b/core/modules/layout_builder/tests/src/Kernel/OverridesSectionStorageTest.php
@@ -19,6 +19,7 @@
  * @coversDefaultClass \Drupal\layout_builder\Plugin\SectionStorage\OverridesSectionStorage
  *
  * @group layout_builder
+ * @group #slow
  */
 class OverridesSectionStorageTest extends KernelTestBase {
 
diff --git a/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php b/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
index 063b0db77cc3e92ddf9171f224a1cac239299b28..e86300d727410a911d6f77620af8d22324c3cb46 100644
--- a/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
+++ b/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
@@ -13,6 +13,7 @@
  * Ensures that media UI works correctly.
  *
  * @group media
+ * @group #slow
  */
 class MediaUiFunctionalTest extends MediaFunctionalTestBase {
 
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php
index 321e2703c691b93e2f93ff6a995e989b50147fe9..03ff94ccc31ec8a28cba87f0c6bd0605649e284d 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php
@@ -7,6 +7,7 @@
 /**
  * @covers ::media_filter_format_edit_form_validate
  * @group media
+ * @group #slow
  */
 class MediaEmbedFilterConfigurationUiTest extends MediaJavascriptTestBase {
 
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d6/Upgrade6Test.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d6/Upgrade6Test.php
index a5e63e57f751d1262c2ff8539c238e2c74388e5f..cc2119a0b2317793ac71e6ae94b26705f342f998 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d6/Upgrade6Test.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d6/Upgrade6Test.php
@@ -11,6 +11,7 @@
  * The test method is provided by the MigrateUpgradeTestBase class.
  *
  * @group migrate_drupal_ui
+ * @group #slow
  */
 class Upgrade6Test extends MigrateUpgradeExecuteTestBase {
 
diff --git a/core/modules/node/tests/src/Functional/NodeTranslationUITest.php b/core/modules/node/tests/src/Functional/NodeTranslationUITest.php
index c4262ffa531d0a1cee135f7f055aaf0aa510ef11..202fcbceae2d341cd52cc0e72f2127612e1e9f3b 100644
--- a/core/modules/node/tests/src/Functional/NodeTranslationUITest.php
+++ b/core/modules/node/tests/src/Functional/NodeTranslationUITest.php
@@ -13,6 +13,7 @@
  * Tests the Node Translation UI.
  *
  * @group node
+ * @group #slow
  */
 class NodeTranslationUITest extends ContentTranslationUITestBase {
 
diff --git a/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php b/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php
index 660bd11f60d38983ecdb8ab25ab213ab1eee8d58..769f2f260bf5e76c272aa9b0137d2f3c540f7e76 100644
--- a/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php
+++ b/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php
@@ -11,6 +11,7 @@
  * Tests the Options widgets.
  *
  * @group options
+ * @group #slow
  */
 class OptionsWidgetsTest extends FieldTestBase {
 
diff --git a/core/modules/page_cache/tests/src/Functional/PageCacheTest.php b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
index a1d9a9ac53b982db20763ab5d4214b2535c8a3f0..9824e196252a14015847517d84effbf2e603b5a6 100644
--- a/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
+++ b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
@@ -15,6 +15,7 @@
  * Enables the page cache and tests it with various HTTP requests.
  *
  * @group page_cache
+ * @group #slow
  */
 class PageCacheTest extends BrowserTestBase {
 
diff --git a/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
index a86ad20e203f7c5082c0dd735508cd613e66f2d9..6a2a42eff1696135560481c426e50bb0a372cf4e 100644
--- a/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
@@ -17,6 +17,7 @@
  * Tests responsive image display formatter.
  *
  * @group responsive_image
+ * @group #slow
  */
 class ResponsiveImageFieldDisplayTest extends ImageFieldTestBase {
 
diff --git a/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php b/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php
index c60693a4dea20bc25d84c523d67cdc146f5cc0d7..7c72ea90ed2d57d718b68fe176b96e25594fca68 100644
--- a/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php
+++ b/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php
@@ -21,6 +21,7 @@
  * Tests the serializer style plugin.
  *
  * @group rest
+ * @group #slow
  * @see \Drupal\rest\Plugin\views\display\RestExport
  * @see \Drupal\rest\Plugin\views\style\Serializer
  * @see \Drupal\rest\Plugin\views\row\DataEntityRow
diff --git a/core/modules/system/tests/src/Functional/Module/DependencyTest.php b/core/modules/system/tests/src/Functional/Module/DependencyTest.php
index 23e49e9441bc92db890fcfc1c3adc6802b3d89c4..aa0cd9bdf840203552618287cff8929198ec37a3 100644
--- a/core/modules/system/tests/src/Functional/Module/DependencyTest.php
+++ b/core/modules/system/tests/src/Functional/Module/DependencyTest.php
@@ -9,6 +9,7 @@
  * Enable module without dependency enabled.
  *
  * @group Module
+ * @group #slow
  */
 class DependencyTest extends ModuleTestBase {
 
diff --git a/core/modules/system/tests/src/Functional/Module/NonStableModulesTest.php b/core/modules/system/tests/src/Functional/Module/NonStableModulesTest.php
index 4250d6350873c601945de06dfe2a3f6c0e9e09cd..239a196eb866ccf419154b470e878fb6e5467327 100644
--- a/core/modules/system/tests/src/Functional/Module/NonStableModulesTest.php
+++ b/core/modules/system/tests/src/Functional/Module/NonStableModulesTest.php
@@ -9,6 +9,7 @@
  * Tests the installation of deprecated and experimental modules.
  *
  * @group Module
+ * @group #slow
  */
 class NonStableModulesTest extends BrowserTestBase {
 
diff --git a/core/modules/system/tests/src/Functional/UpdateSystem/UpdateScriptTest.php b/core/modules/system/tests/src/Functional/UpdateSystem/UpdateScriptTest.php
index 764df74e68583db0b99f5a257451fce1dd2b550c..0db7654cf2982b12a9b5452c05b2b463b282caad 100644
--- a/core/modules/system/tests/src/Functional/UpdateSystem/UpdateScriptTest.php
+++ b/core/modules/system/tests/src/Functional/UpdateSystem/UpdateScriptTest.php
@@ -12,6 +12,7 @@
  * Tests the update script access and functionality.
  *
  * @group Update
+ * @group #slow
  */
 class UpdateScriptTest extends BrowserTestBase {
 
diff --git a/core/modules/update/tests/src/Functional/UpdateContribTest.php b/core/modules/update/tests/src/Functional/UpdateContribTest.php
index 41f20ccff2ab22485fe2f3fb38e35d0e9ed9a51e..aa753e74684522d3820e9ff8a90fcaa40b48a3f5 100644
--- a/core/modules/update/tests/src/Functional/UpdateContribTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateContribTest.php
@@ -9,6 +9,7 @@
  * Tests how the Update Manager handles contributed modules and themes.
  *
  * @group update
+ * @group #slow
  */
 class UpdateContribTest extends UpdateTestBase {
   use UpdateTestTrait;
diff --git a/core/modules/update/tests/src/Functional/UpdateSemverContribTest.php b/core/modules/update/tests/src/Functional/UpdateSemverContribTest.php
index 213d6e1ce80b537bd7e704863a9f64d398ef9970..a59b4545da6a3e1aad919dbc37639dc577d530a5 100644
--- a/core/modules/update/tests/src/Functional/UpdateSemverContribTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateSemverContribTest.php
@@ -6,6 +6,7 @@
  * Tests the Update Manager module with a contrib module with semver versions.
  *
  * @group update
+ * @group #slow
  */
 class UpdateSemverContribTest extends UpdateSemverTestBase {
   use UpdateTestTrait;
diff --git a/core/modules/update/tests/src/Functional/UpdateSemverCoreTest.php b/core/modules/update/tests/src/Functional/UpdateSemverCoreTest.php
index 8fe8fbe3f24c97b1ff02fd8a31920ae5a18f648e..333a5c9c958d1097ca28e8b62e5eef31a5c0f505 100644
--- a/core/modules/update/tests/src/Functional/UpdateSemverCoreTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateSemverCoreTest.php
@@ -8,6 +8,7 @@
  * Tests the semantic version handling in the Update Manager.
  *
  * @group update
+ * @group #slow
  */
 class UpdateSemverCoreTest extends UpdateSemverTestBase {
   use UpdateTestTrait;
diff --git a/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php b/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
index 99bfb6baabf5c8538e8e0eeb26d96441d9dbfe3b..dc5f4fa9ee57f9f16eb3cee9145a0c7fbc6f0b2c 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
@@ -15,6 +15,7 @@
  * Tests exposed forms functionality.
  *
  * @group views
+ * @group #slow
  */
 class ExposedFormTest extends ViewTestBase {
 
diff --git a/core/modules/views/tests/src/Kernel/EventSubscriber/ViewsEntitySchemaSubscriberIntegrationTest.php b/core/modules/views/tests/src/Kernel/EventSubscriber/ViewsEntitySchemaSubscriberIntegrationTest.php
index 8f7f5307359c69a28bdf2a38c361ed1069705099..c5db2717eae179fd9931f1746089c78d33c2a4dd 100644
--- a/core/modules/views/tests/src/Kernel/EventSubscriber/ViewsEntitySchemaSubscriberIntegrationTest.php
+++ b/core/modules/views/tests/src/Kernel/EventSubscriber/ViewsEntitySchemaSubscriberIntegrationTest.php
@@ -12,6 +12,7 @@
  * Tests \Drupal\views\EventSubscriber\ViewsEntitySchemaSubscriber.
  *
  * @group Views
+ * @group #slow
  */
 class ViewsEntitySchemaSubscriberIntegrationTest extends ViewsKernelTestBase {
 
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php b/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php
index d893234e4db3e70781c627d90cde99791dc92c1e..458cab3e06f23000dd995d732bef787d878b5711 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php
@@ -18,6 +18,7 @@
  *
  * @see \Drupal\views\Plugin\views\field\EntityField
  * @group views
+ * @group #slow
  */
 class FieldFieldTest extends ViewsKernelTestBase {
 
diff --git a/core/modules/views/tests/src/Kernel/Handler/FilterNumericTest.php b/core/modules/views/tests/src/Kernel/Handler/FilterNumericTest.php
index cfef9d458cd79ac6bf4f93e223f8c60156aa1287..ab7cef8c83903b4177ae7329bdd4d52a1f378400 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FilterNumericTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FilterNumericTest.php
@@ -9,6 +9,7 @@
  * Tests the numeric filter handler.
  *
  * @group views
+ * @group #slow
  */
 class FilterNumericTest extends ViewsKernelTestBase {
 
diff --git a/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php b/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php
index 45f443af95341a421e0bd0b635ec95ca3a6b1ad0..b36a34d22205fddf20cec3b09bdd499d8b219072 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FilterStringTest.php
@@ -9,6 +9,7 @@
  * Tests the core Drupal\views\Plugin\views\filter\StringFilter handler.
  *
  * @group views
+ * @group #slow
  */
 class FilterStringTest extends ViewsKernelTestBase {
 
diff --git a/core/modules/views/tests/src/Kernel/QueryGroupByTest.php b/core/modules/views/tests/src/Kernel/QueryGroupByTest.php
index 20a55769fbd540b6bc4d9809fd024d2a30b787d1..522ff701ca66122237114d6dfaff3052b070ccfc 100644
--- a/core/modules/views/tests/src/Kernel/QueryGroupByTest.php
+++ b/core/modules/views/tests/src/Kernel/QueryGroupByTest.php
@@ -13,6 +13,7 @@
  * Tests aggregate functionality of views, for example count.
  *
  * @group views
+ * @group #slow
  */
 class QueryGroupByTest extends ViewsKernelTestBase {
 
diff --git a/core/modules/views/tests/src/Kernel/ViewExecutableTest.php b/core/modules/views/tests/src/Kernel/ViewExecutableTest.php
index f44cdc15a0d0a8848976a5fe0b62a648c6a9e93f..4e6d651b1877b616f37c4756383212ce4d9f4f64 100644
--- a/core/modules/views/tests/src/Kernel/ViewExecutableTest.php
+++ b/core/modules/views/tests/src/Kernel/ViewExecutableTest.php
@@ -27,6 +27,7 @@
  * Tests the ViewExecutable class.
  *
  * @group views
+ * @group #slow
  * @see \Drupal\views\ViewExecutable
  */
 class ViewExecutableTest extends ViewsKernelTestBase {
diff --git a/core/modules/workflows/tests/src/Kernel/WorkflowAccessControlHandlerTest.php b/core/modules/workflows/tests/src/Kernel/WorkflowAccessControlHandlerTest.php
index 3b1ae3426531f33b2bc9660d9c549bcc693657b3..df8496182127c8a5fb98f473bb4358e41fef8e17 100644
--- a/core/modules/workflows/tests/src/Kernel/WorkflowAccessControlHandlerTest.php
+++ b/core/modules/workflows/tests/src/Kernel/WorkflowAccessControlHandlerTest.php
@@ -13,6 +13,7 @@
 /**
  * @coversDefaultClass \Drupal\workflows\WorkflowAccessControlHandler
  * @group workflows
+ * @group #slow
  */
 class WorkflowAccessControlHandlerTest extends KernelTestBase {
 
diff --git a/core/modules/workflows/tests/src/Kernel/WorkflowValidationTest.php b/core/modules/workflows/tests/src/Kernel/WorkflowValidationTest.php
index a3448a1a10cad69564d79631d9e3c477503a2710..5f1c558e893fe0b2b494939a62bc8c69fd17c2a9 100644
--- a/core/modules/workflows/tests/src/Kernel/WorkflowValidationTest.php
+++ b/core/modules/workflows/tests/src/Kernel/WorkflowValidationTest.php
@@ -9,6 +9,7 @@
  * Tests validation of workflow entities.
  *
  * @group workflows
+ * @group #slow
  */
 class WorkflowValidationTest extends ConfigEntityValidationTestBase {
 
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
index f8080e8f76a9dd2a9f418253aeb6d36baabf1c07..524413750b58a639c7aaa3482a556ce7bc73a4c5 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
@@ -11,6 +11,7 @@
  * Test the workspace entity.
  *
  * @group workspaces
+ * @group #slow
  */
 class WorkspaceTest extends BrowserTestBase {
 
diff --git a/core/profiles/demo_umami/tests/src/Functional/DemoUmamiProfileTest.php b/core/profiles/demo_umami/tests/src/Functional/DemoUmamiProfileTest.php
index 6b831095fe0fdc691ff3b31098c1dc1523070388..b10365697d26ad2502fdec9f6b9e6c6565f92121 100644
--- a/core/profiles/demo_umami/tests/src/Functional/DemoUmamiProfileTest.php
+++ b/core/profiles/demo_umami/tests/src/Functional/DemoUmamiProfileTest.php
@@ -18,6 +18,7 @@
  * Tests demo_umami profile.
  *
  * @group demo_umami
+ * @group #slow
  */
 class DemoUmamiProfileTest extends BrowserTestBase {
   use AssertConfigTrait;
diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index 5317ba5a655d66655cd0aeec9416d760c2abf307..cc5b830f4104e6c89dbac3323db0174a1471259e 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -898,6 +898,7 @@ function simpletest_script_get_test_list() {
   );
   $types_processed = empty($args['types']);
   $test_list = [];
+  $slow_tests = [];
   if ($args['all'] || $args['module']) {
     try {
       $groups = $test_discovery->getTestClasses($args['module'], $args['types']);
@@ -907,11 +908,17 @@ function simpletest_script_get_test_list() {
       echo (string) $e;
       exit(SIMPLETEST_SCRIPT_EXIT_EXCEPTION);
     }
+    if ((int) $args['ci-parallel-node-total'] > 1) {
+      if (key($groups) === '#slow') {
+        $slow_tests = array_keys(array_shift($groups));
+      }
+    }
     $all_tests = [];
     foreach ($groups as $group => $tests) {
       $all_tests = array_merge($all_tests, array_keys($tests));
     }
     $test_list = array_unique($all_tests);
+    $test_list = array_diff($test_list, $slow_tests);
   }
   else {
     if ($args['class']) {
@@ -1028,8 +1035,9 @@ function simpletest_script_get_test_list() {
   }
 
   if ((int) $args['ci-parallel-node-total'] > 1) {
+    $slow_tests_per_job = ceil(count($slow_tests) / $args['ci-parallel-node-total']);
     $tests_per_job = ceil(count($test_list) / $args['ci-parallel-node-total']);
-    $test_list = array_slice($test_list, ($args['ci-parallel-node-index'] - 1) * $tests_per_job, $tests_per_job);
+    $test_list = array_merge(array_slice($slow_tests, ($args['ci-parallel-node-index'] -1) * $slow_tests_per_job, $slow_tests_per_job), array_slice($test_list, ($args['ci-parallel-node-index'] - 1) * $tests_per_job, $tests_per_job));
   }
 
   return $test_list;
diff --git a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
index 84782f74185949818b78ff57a26e71259da67c76..e9cd2e70adb6ec1cc7cc239802e2c4b8ce123e2b 100644
--- a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
+++ b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
@@ -16,6 +16,7 @@
  * Tests BrowserTestBase functionality.
  *
  * @group browsertestbase
+ * @group #slow
  */
 class BrowserTestBaseTest extends BrowserTestBase {
 
diff --git a/core/tests/Drupal/FunctionalTests/Entity/RevisionVersionHistoryTest.php b/core/tests/Drupal/FunctionalTests/Entity/RevisionVersionHistoryTest.php
index 32cf997b9904fba92a5ec9b19f0290b9de951b0b..ee7041c43fbad558513dc43ce4efd4cf2da82b41 100644
--- a/core/tests/Drupal/FunctionalTests/Entity/RevisionVersionHistoryTest.php
+++ b/core/tests/Drupal/FunctionalTests/Entity/RevisionVersionHistoryTest.php
@@ -11,6 +11,7 @@
  * Tests version history page.
  *
  * @group Entity
+ * @group #slow
  * @coversDefaultClass \Drupal\Core\Entity\Controller\VersionHistoryController
  */
 class RevisionVersionHistoryTest extends BrowserTestBase {
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
index 261763b142073cdc78d082dc9b77f77e5cbde3d0..a293e1a2399b73096ac0969bcabdc565ef4d53b6 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
@@ -25,6 +25,7 @@
  * @coversDefaultClass \Drupal\Core\Entity\EntityDefinitionUpdateManager
  *
  * @group Entity
+ * @group #slow
  */
 class EntityDefinitionUpdateTest extends EntityKernelTestBase {
 
diff --git a/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php b/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
index 817e4e2698a358514fc1f89995cabe5487b54df4..b38371d4a4f647fe7c882ca9aa6a9b12dafe7a61 100644
--- a/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
@@ -12,6 +12,7 @@
  *
  * @coversDefaultClass \Drupal\system\Plugin\ImageToolkit\GDToolkit
  * @group Image
+ * @group #slow
  * @requires extension gd
  */
 class ToolkitGdTest extends KernelTestBase {
diff --git a/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php b/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
index ca05d32c7730be014bb944ad1cdc5d734ea2d270..9d9119f7b579cbcad5c61cd8231555af18a90798 100644
--- a/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
+++ b/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
@@ -62,7 +62,7 @@ public function infoParserProvider() {
       [
         'name' => 'Drupal\FunctionalTests\BrowserTestBaseTest',
         'group' => 'browsertestbase',
-        'groups' => ['browsertestbase'],
+        'groups' => ['browsertestbase', '#slow'],
         'description' => 'Tests BrowserTestBase functionality.',
         'type' => 'PHPUnit-Functional',
       ],