diff -u b/core/lib/Drupal/Component/Utility/Html.php b/core/lib/Drupal/Component/Utility/Html.php
--- b/core/lib/Drupal/Component/Utility/Html.php
+++ b/core/lib/Drupal/Component/Utility/Html.php
@@ -102,16 +102,6 @@
   }
 
   /**
-   * Sets the AJAX HTML IDs.
-   *
-   * @param string $ajax_html_ids
-   *   The AJAX HTML IDs, probably coming from the current request.
-   */
-  public static function setAjaxHtmlIds($ajax_html_ids = '') {
-    static::$ajaxHTMLIDs = $ajax_html_ids;
-  }
-
-  /**
    * Prepares a string for use as a valid HTML ID and guarantees uniqueness.
    *
    * This function ensures that each passed HTML ID value only exists once on
@@ -149,7 +139,7 @@
     }
 
     $id .= '-' . $request_nonce;
-    return $id;
+    return Html::getId($id);
   }
 
   /**
@@ -183,13 +173,6 @@
   }
 
   /**
-   * Resets the list of seen IDs.
-   */
-  public static function resetSeenIds() {
-    static::$seenIds = NULL;
-  }
-
-  /**
    * Normalizes an HTML snippet.
    *
    * This function is essentially \DOMDocument::normalizeDocument(), but
diff -u b/core/modules/views_ui/src/ViewUI.php b/core/modules/views_ui/src/ViewUI.php
--- b/core/modules/views_ui/src/ViewUI.php
+++ b/core/modules/views_ui/src/ViewUI.php
@@ -423,10 +423,6 @@
    * rather than closing the ajax popup.
    */
   public function addFormToStack($key, $display_id, $type, $id = NULL, $top = FALSE, $rebuild_keys = FALSE) {
-    // Reset the cache of IDs. Drupal rather aggressively prevents ID
-    // duplication but this causes it to remember IDs that are no longer even
-    // being used.
-    Html::resetSeenIds();
 
     if (empty($this->stack)) {
       $this->stack = array();
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -468,16 +468,6 @@ public function processForm($form_id, &$form, FormStateInterface &$form_state) {
       }
       $this->formValidator->validateForm($form_id, $form, $form_state);
 
-      // drupal_html_id() maintains a cache of element IDs it has seen, so it
-      // can prevent duplicates. We want to be sure we reset that cache when a
-      // form is processed, so scenarios that result in the form being built
-      // behind the scenes and again for the browser don't increment all the
-      // element IDs needlessly.
-      if (!FormState::hasAnyErrors()) {
-        // In case of errors, do not break HTML IDs of other forms.
-        Html::resetSeenIds();
-      }
-
       if (!$form_state->isRebuilding() && !FormState::hasAnyErrors()) {
         if ($submit_response = $this->formSubmitter->doSubmitForm($form, $form_state)) {
           return $submit_response;
only in patch2:
unchanged:
--- a/core/modules/block/src/Tests/BlockViewBuilderTest.php
+++ b/core/modules/block/src/Tests/BlockViewBuilderTest.php
@@ -92,9 +92,6 @@ public function testBasicRendering() {
     $expected_output = implode("\n", $expected);
     $this->assertEqual(drupal_render($output), $expected_output);
 
-    // Reset the HTML IDs so that the next render is not affected.
-    Html::resetSeenIds();
-
     // Test the rendering of a block with a given title.
     $entity = $this->controller->create(array(
       'id' => 'test_block2',
only in patch2:
unchanged:
--- a/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php
+++ b/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php
@@ -90,11 +90,6 @@ public function getForm(ViewStorageInterface $view, $display_id, $js) {
     \Drupal::moduleHandler()->loadInclude('views_ui', 'inc', 'admin');
     \Drupal::moduleHandler()->loadInclude('views', 'inc', 'includes/ajax');
 
-    // Reset the cache of IDs. Drupal rather aggressively prevents ID
-    // duplication but this causes it to remember IDs that are no longer even
-    // being used.
-    Html::resetSeenIds();
-
     // check to see if this is the top form of the stack. If it is, pop
     // it off; if it isn't, the user clicked somewhere else and the stack is
     // now irrelevant.
only in patch2:
unchanged:
--- a/core/tests/Drupal/Tests/Core/Form/FormTestBase.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormTestBase.php
@@ -167,13 +167,6 @@ protected function setUp() {
   }
 
   /**
-   * {@inheritdoc}
-   */
-  protected function tearDown() {
-    Html::resetSeenIds();
-  }
-
-  /**
    * Provides a mocked form object.
    *
    * @param string $form_id
only in patch2:
unchanged:
--- a/core/tests/Drupal/Tests/Core/Utility/HtmlTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/HtmlTest.php
@@ -100,17 +100,11 @@ public function testHtmlClass() {
    *   The expected result.
    * @param string $source
    *   The string being transformed to an ID.
-   * @param bool $reset
-   *   (optional) If TRUE, reset the list of seen IDs. Defaults to FALSE.
-   *
    * @dataProvider providerTestHtmlGetUniqueId
    *
    * @covers ::getUniqueId
    */
-  public function testHtmlGetUniqueId($expected, $source, $reset = FALSE) {
-    if ($reset) {
-      Html::resetSeenIds();
-    }
+  public function testHtmlGetUniqueId($expected, $source) {
     $this->assertSame($expected, Html::getUniqueId($source));
   }
 
@@ -143,18 +137,12 @@ public function providerTestHtmlGetUniqueId() {
    *   The expected result.
    * @param string $source
    *   The string being transformed to an ID.
-   * @param bool $reset
-   *   (optional) If TRUE, reset the list of seen IDs. Defaults to FALSE.
    *
    * @dataProvider providerTestHtmlGetUniqueIdWithAjaxIds
    *
    * @covers ::getUniqueId
    */
-  public function testHtmlGetUniqueIdWithAjaxIds($expected, $source, $reset = FALSE) {
-    if ($reset) {
-      Html::resetSeenIds();
-    }
-    Html::setAjaxHtmlIds('test-unique-id1 test-unique-id2--3');
+  public function testHtmlGetUniqueIdWithAjaxIds($expected, $source) {
     $this->assertSame($expected, Html::getUniqueId($source));
   }