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 cfc25a416f62a5340e3248bafcc4bf07199eea04..fb9820657b1ce4c68789bd3f325918500074c981 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 7117260c4c94049ecb03fcaea39419c70f6c696f..9681e91a705ef2c7091aa0057b62ba1d6e2e940f 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 c04c0eb9acaca1ee615f159d6c007eb2c60a3736..62c84cb68433e7cc38682cb58f343c0a4312ca2e 100644
--- a/core/modules/config/tests/src/Functional/ConfigImportAllTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigImportAllTest.php
@@ -12,6 +12,7 @@
  * Tests the largest configuration import possible with all available modules.
  *
  * @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 0371c396853dbd651ac5abeac8e8e5af1dcc6757..9883d2a20c3c80ed554d9d52b01f5ef6b954b20b 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 f63fa159443cf7ae6561793f237283617f897237..d62f26b51e1ce387c9a7ff0d1bef860dca0ad2c6 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 85e2d8a1b2cc1ac8dc504827ff0b8679a058de49..0979503655df0b054c76cd8edfbbb7f3566bde18 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 5235a3e457caaa2fa2bdb9ac1442969180fb63bb..1f68ba8fd34a198e8cc3d473be22544e9d82460f 100644
--- a/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
+++ b/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
@@ -20,6 +20,7 @@
  * 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 a779ca9a0ec546b3b55179977962bc1f50153ea7..e657dfc863b0ee3683b3c1ac81654e2984651e95 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 fc274647fa815a1c5089066164656a1f2146a2ec..3ee26c15d76b575d91bfef9ccb12ad22dbab3c12 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 01a2e6a77ed9782ff00016327b0579a673357125..d0eed791a68c4fe8789405075b95d7ccfab91723 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 6a8382bf6e77e01c9ed1754c25f84c5f60a12ae3..02d149ef72f0cb7c9ecd4d5cbd62096dad57bf1b 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
@@ -12,6 +12,7 @@
  * 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 362467b3807ca354d7b3abd428dea67491709c02..01a873ab9ad7cef3906746b7bbd3a706b893b096 100644
--- a/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
+++ b/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
@@ -12,6 +12,7 @@
  * 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 1e6249c2e27f281c6dfa7f1bd8fcc97d697b91a6..b409c09a568c3485bd57dd8f9059b49905458d11 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 efbef09f13f4fcc411944304de3ae681f5399433..9613fe09fa006a0e53f03e00dd009b90b2391f8f 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 6e09777e86fd55b44818d6879baa2212d4743dd2..5c58d7a97dd0bd221f2f9ed536be84d58cddb944 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 c99ee3084a6edb7c3c36322eea2b3018ad5c53f3..a8dc40c48307b21eec77ce76da9a6f5777974d75 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 0cf0012d4166b9d65799b3d007e8d3d2d90fe275..add35fcac419a366fd3668fdce8d008f5ae04479 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 9a71aba4f2f3e43196350b802724ed85542aae56..02e969b129cfb61193a792aeac241082d97e8bdd 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 294074c592e92f47bd51a8751e0d4602cd8e3e8f..5bf393afb449b001eb9d249e211eb7e760346f36 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 {
 
diff --git a/core/modules/update/tests/src/Functional/UpdateSemverContribTest.php b/core/modules/update/tests/src/Functional/UpdateSemverContribTest.php
index 6d884973084df0aadc6c3a1251319f3457440ac2..8f18a00eb618569031c39f41ce16e059765900d7 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 {
 
diff --git a/core/modules/update/tests/src/Functional/UpdateSemverCoreTest.php b/core/modules/update/tests/src/Functional/UpdateSemverCoreTest.php
index 829b68dd7b308d8ef86bdc150eab855edb01cff7..00e8ffb8663dec4f6ac74dcfad33fd9caea1cf32 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 {
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php b/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
index 4f6dd5b8446013c37ed51fc8ad3b59193b418987..d24a4f5b324172d792e34fd4ef8f5b2b81de3cc9 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
@@ -14,6 +14,7 @@
  * 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 4c3741b300931d7d74a01f0c460a303e2fbf30c6..b9a56b6b4fb83a239104b96736c2ffff7a4c8524 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 98e058763feaed805c92881e10566c82b8781519..28c56dc2b86d2a06d79e39456d044614189a5247 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 c65e49dd0a4acb06d61c4220946112a5bcd53c10..e56aaa351a5854b8dd3f097549278cbd540e9f41 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 65e800c83de661e8780062a1b4e417bc26bb5290..bf21647424481c7197c54261905e71a7d1c0a45b 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
@@ -10,6 +10,7 @@
  * 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 d82bede726ddbe315fad0c64667ceaa515f89cc3..c255e450133f1a5259947255dcf7d71405791ac7 100644
--- a/core/profiles/demo_umami/tests/src/Functional/DemoUmamiProfileTest.php
+++ b/core/profiles/demo_umami/tests/src/Functional/DemoUmamiProfileTest.php
@@ -14,6 +14,7 @@
  * 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 e84e3ad336b669914ff6039a93b6fd9aac4a44dd..19766d2a19e178c0e81e1166352bfc6e041f8718 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 28ea85730eb0caa43d7af827782157104273da39..423bac6e3f2304322f9a8de409913a085b9b5aa8 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 b332eccfe6b4fb4fa19d98e83cc31e7913e19ac7..4fce6fe49a26cc9831f9edbaebf80ff52b9ffc96 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',
       ],