46 files declare their use of Block

AreaEntityUITest.php in core/modules/views_ui/tests/src/Functional/AreaEntityUITest.php
AssertBlockAppearsTrait.php in core/modules/block/tests/src/Functional/AssertBlockAppearsTrait.php
BigPipeInterfacePreviewThemeSuggestionsTest.php in core/modules/big_pipe/tests/src/Kernel/BigPipeInterfacePreviewThemeSuggestionsTest.php
block.module in core/modules/block/block.module
Controls the visual building blocks a page is constructed with.
BlockConfigSchemaTest.php in core/modules/book/tests/src/Kernel/Block/BlockConfigSchemaTest.php
BlockConfigSchemaTest.php in core/modules/block/tests/src/Kernel/BlockConfigSchemaTest.php
BlockContentTest.php in core/modules/block_content/tests/src/Kernel/BlockContentTest.php
BlockCreationTrait.php in core/modules/block/tests/src/Traits/BlockCreationTrait.php
BlockDependenciesTest.php in core/modules/views/tests/src/Kernel/Plugin/BlockDependenciesTest.php
BlockFormTest.php in core/modules/block/tests/src/Unit/BlockFormTest.php
BlockInvalidRegionTest.php in core/modules/block/tests/src/Functional/BlockInvalidRegionTest.php
BlockLanguageTest.php in core/modules/block/tests/src/Functional/BlockLanguageTest.php
BlockRebuildTest.php in core/modules/block/tests/src/Kernel/BlockRebuildTest.php
BlockResourceTestBase.php in core/modules/block/tests/src/Functional/Rest/BlockResourceTestBase.php
BlockStorageUnitTest.php in core/modules/block/tests/src/Kernel/BlockStorageUnitTest.php
BlockTemplateSuggestionsTest.php in core/modules/block_content/tests/src/Kernel/BlockTemplateSuggestionsTest.php
BlockTemplateSuggestionsTest.php in core/modules/block/tests/src/Kernel/BlockTemplateSuggestionsTest.php
BlockTest.php in core/modules/block/tests/src/Functional/BlockTest.php
BlockTest.php in core/modules/jsonapi/tests/src/Functional/BlockTest.php
BlockValidationTest.php in core/modules/block/tests/src/Kernel/BlockValidationTest.php
BlockViewBuilder.php in core/modules/block/src/BlockViewBuilder.php
BlockViewBuilderTest.php in core/modules/block/tests/src/Kernel/BlockViewBuilderTest.php
BreadcrumbTest.php in core/modules/system/tests/src/Functional/Menu/BreadcrumbTest.php
EntityCrudHookTest.php in core/tests/Drupal/KernelTests/Core/Entity/EntityCrudHookTest.php
HelpTopicsMerge.php in core/modules/help/tests/src/Functional/Update/HelpTopicsMerge.php
InstallerThemesBlocksProfileTest.php in core/tests/Drupal/FunctionalTests/Installer/InstallerThemesBlocksProfileTest.php
LanguageUILanguageNegotiationTest.php in core/modules/language/tests/src/Functional/LanguageUILanguageNegotiationTest.php
LocaleConfigManagerTest.php in core/modules/locale/tests/src/Kernel/LocaleConfigManagerTest.php
MappingTest.php in core/tests/Drupal/KernelTests/Config/Schema/MappingTest.php
MenuBlockTest.php in core/modules/menu_ui/tests/src/Kernel/MenuBlockTest.php
MenuUiTest.php in core/modules/menu_ui/tests/src/Functional/MenuUiTest.php
MigrateBlockNoBlockContentTest.php in core/modules/block/tests/src/Kernel/Migrate/d7/MigrateBlockNoBlockContentTest.php
MigrateBlockTest.php in core/modules/block/tests/src/Kernel/Migrate/d7/MigrateBlockTest.php
MigrateBlockTest.php in core/modules/forum/tests/src/Kernel/Migrate/d6/MigrateBlockTest.php
MigrateBlockTest.php in core/modules/block/tests/src/Kernel/Migrate/d6/MigrateBlockTest.php
NavigationMenuBlockTest.php in core/modules/navigation/tests/src/Kernel/NavigationMenuBlockTest.php
NodeBlockFunctionalTest.php in core/modules/node/tests/src/Functional/NodeBlockFunctionalTest.php
OverriddenConfigurationTest.php in core/modules/settings_tray/tests/src/FunctionalJavascript/OverriddenConfigurationTest.php
SettingsTrayTest.php in core/modules/settings_tray/tests/src/Functional/SettingsTrayTest.php
SettingsTrayTestBase.php in core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayTestBase.php
settings_tray.module in core/modules/settings_tray/settings_tray.module
Allows configuring blocks and other configuration from the site front-end.
SystemMenuBlockTest.php in core/modules/system/tests/src/Kernel/Block/SystemMenuBlockTest.php
SystemMenuNavigationBlockTest.php in core/modules/navigation/tests/src/Kernel/SystemMenuNavigationBlockTest.php
ValidKeysConstraintValidatorTest.php in core/tests/Drupal/KernelTests/Core/TypedData/ValidKeysConstraintValidatorTest.php
ViewsBlockTest.php in core/modules/views_ui/tests/src/Kernel/ViewsBlockTest.php
WhoIsOnlineBlockTest.php in core/modules/user/tests/src/Kernel/WhoIsOnlineBlockTest.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.