37 files declare their use of UrlHelper

batch.inc in core/includes/batch.inc
Batch processing API for processes to run in multiple HTTP requests.
BigPipeStrategy.php in core/modules/big_pipe/src/Render/Placeholder/BigPipeStrategy.php
BigPipeTest.php in core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
ConfirmFormHelper.php in core/lib/Drupal/Core/Form/ConfirmFormHelper.php
contextual.module in core/modules/contextual/contextual.module
Adds contextual links to perform actions related to elements on a page.
ContextualLinks.php in core/modules/contextual/src/Plugin/views/field/ContextualLinks.php
Cookie.php in core/modules/user/src/Authentication/Provider/Cookie.php
CustomPageExceptionHtmlSubscriberTest.php in core/tests/Drupal/Tests/Core/EventSubscriber/CustomPageExceptionHtmlSubscriberTest.php
DrupalKernel.php in core/lib/Drupal/Core/DrupalKernel.php
FileUrlGenerator.php in core/lib/Drupal/Core/File/FileUrlGenerator.php
form.inc in core/includes/form.inc
Functions for form and batch generation and processing.
FormattableMarkup.php in core/lib/Drupal/Component/Render/FormattableMarkup.php
FormBuilder.php in core/lib/Drupal/Core/Form/FormBuilder.php
GotoAction.php in core/lib/Drupal/Core/Action/Plugin/Action/GotoAction.php
install.core.inc in core/includes/install.core.inc
API functions for installing Drupal.
install.inc in core/includes/install.inc
API functions for installing modules and themes.
LocalAwareRedirectResponseTrait.php in core/lib/Drupal/Core/Routing/LocalAwareRedirectResponseTrait.php
MenuTreeStorage.php in core/lib/Drupal/Core/Menu/MenuTreeStorage.php
PagerParameters.php in core/lib/Drupal/Core/Pager/PagerParameters.php
PathValidator.php in core/lib/Drupal/Core/Path/PathValidator.php
PlaceholderGenerator.php in core/lib/Drupal/Core/Render/PlaceholderGenerator.php
PublicStream.php in core/lib/Drupal/Core/StreamWrapper/PublicStream.php
RedirectDestination.php in core/lib/Drupal/Core/Routing/RedirectDestination.php
RedirectDestinationTest.php in core/tests/Drupal/Tests/Core/Routing/RedirectDestinationTest.php
RedirectResponseSubscriber.php in core/lib/Drupal/Core/EventSubscriber/RedirectResponseSubscriber.php
RequestSanitizer.php in core/lib/Drupal/Core/Security/RequestSanitizer.php
TableSort.php in core/lib/Drupal/Core/Utility/TableSort.php
UiHelperTrait.php in core/tests/Drupal/Tests/UiHelperTrait.php
UnroutedUrlAssembler.php in core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
Url.php in core/lib/Drupal/Core/Url.php
Url.php in core/lib/Drupal/Core/Render/Element/Url.php
UrlGenerator.php in core/lib/Drupal/Core/Routing/UrlGenerator.php
UrlHelperTest.php in core/tests/Drupal/Tests/Component/Utility/UrlHelperTest.php
UrlTest.php in core/tests/Drupal/Tests/Core/UrlTest.php
Contains \Drupal\Tests\Core\UrlTest.
UserLoginBlock.php in core/modules/user/src/Plugin/Block/UserLoginBlock.php
XssTest.php in core/tests/Drupal/Tests/Component/Utility/XssTest.php
XssUnitTest.php in core/tests/Drupal/KernelTests/Core/Common/XssUnitTest.php

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