diff --git a/core/modules/filter/src/Plugin/Filter/FilterHtml.php b/core/modules/filter/src/Plugin/Filter/FilterHtml.php
index 38d798a7a148a6a4821347f05bfa2a4808550123..1baf73c62aaa32ed7316263bcc7c8c2bebef6470 100644
--- a/core/modules/filter/src/Plugin/Filter/FilterHtml.php
+++ b/core/modules/filter/src/Plugin/Filter/FilterHtml.php
@@ -50,7 +50,7 @@ public function settingsForm(array $form, FormStateInterface $form_state) {
       '#title' => $this->t('Allowed HTML tags'),
       '#default_value' => $this->settings['allowed_html'],
       '#maxlength' => 1024,
-      '#description' => $this->t('A list of HTML tags that can be used. JavaScript event attributes, JavaScript URLs, and CSS are always stripped.'),
+      '#description' => $this->t('A list of HTML tags that can be used. By default only the <em>lang</em> and <em>dir</em> attributes are allowed for all HTML tags. Each HTML tag may have attributes which are treated as allowed attribute names for that HTML tag. Each attribute may allow all values, or only allow specific values. Attribute names or values may be written as a prefix and wildcard like <em>jump-*</em>. JavaScript event attributes, JavaScript URLs, and CSS are always stripped.'),
       '#size' => 250,
       '#attached' => array(
         'library' => array(