diff --git a/config/schema/smart_trim.schema.yml b/config/schema/smart_trim.schema.yml
index 10d42e7..7adacd9 100644
--- a/config/schema/smart_trim.schema.yml
+++ b/config/schema/smart_trim.schema.yml
@@ -55,3 +55,6 @@ field.formatter.settings.smart_trim:
         replace_tokens:
           type: boolean
           label: 'Replace tokens before trimming'
+    trim_options_allowed_html:
+      type: mapping
+      label: 'Allowed HTML tags'
diff --git a/smart_trim.module b/smart_trim.module
index b0257ea..a847e1e 100644
--- a/smart_trim.module
+++ b/smart_trim.module
@@ -5,6 +5,7 @@
  * Nothing to see here. It's all about the Field/FieldFormatter.
  */
 
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
 
 /**
@@ -20,6 +21,26 @@ function smart_trim_help($route_name, RouteMatchInterface $route_match): string
   return $output;
 }
 
+/**
+ * Change tags from string to array to speed up the formatter view.
+ *
+ * @param array $element
+ *   Form element.
+ *
+ * @param array $form_state
+ *   Form state.
+ */
+function _smart_trim_validate_allowed_html($element, FormStateInterface $form_state) {
+  $tags  = array();
+  $value = isset($element['#value']) ? trim($element['#value']) : '';
+
+  if (!empty($value)) {
+    $tags = preg_split('/\s+|<|>/', $value, -1, PREG_SPLIT_NO_EMPTY);
+  }
+
+  $form_state->setValue($element['#parents'], $tags);
+}
+
 /**
  * Implements hook_theme().
  */
diff --git a/src/Plugin/Field/FieldFormatter/SmartTrimFormatter.php b/src/Plugin/Field/FieldFormatter/SmartTrimFormatter.php
index d4bcdd5..ac28748 100644
--- a/src/Plugin/Field/FieldFormatter/SmartTrimFormatter.php
+++ b/src/Plugin/Field/FieldFormatter/SmartTrimFormatter.php
@@ -11,6 +11,7 @@ use Drupal\smart_trim\TruncateHTML;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Drupal\Core\Utility\Token;
 use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Component\Utility\Xss;
 
 /**
  * Plugin implementation of the 'smart_trim' formatter.
@@ -119,6 +120,7 @@ class SmartTrimFormatter extends FormatterBase implements ContainerFactoryPlugin
       ],
       'summary_handler' => 'full',
       'trim_options' => [],
+      'trim_options_allowed_html' => [],
     ] + parent::defaultSettings();
   }
 
@@ -278,6 +280,32 @@ class SmartTrimFormatter extends FormatterBase implements ContainerFactoryPlugin
       '#states' => $more_states,
     ];
 
+    $allowed_html = $this->getSetting('trim_options_allowed_html');
+
+    if (empty($allowed_html)) {
+      $tags = '';
+    }
+    elseif (is_string($allowed_html)) {
+      $tags = $allowed_html;
+    }
+    else {
+      $tags = '<' . implode('> <', $allowed_html) . '>';
+    }
+
+    $element['trim_options_allowed_html'] = [
+      '#title' => $this->t('Allowed HTML tags'),
+      '#type' => 'textfield',
+      '#size' => 20,
+      '#default_value' => $tags,
+      '#description' => $this->t('See <a href="@link" target="_blank">Xss::filter()</a> for more information', ['@link' => 'https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Component%21Utility%21Xss.php/function/Xss%3A%3Afilter']),
+      '#element_validate' => ['_smart_trim_validate_allowed_html'],
+      '#states' => [
+        'visible' => [
+          ':input[name="fields[body][settings_edit_form][settings][trim_options][text]"]' => ['checked' => TRUE],
+        ],
+      ],
+    ];
+
     return $element;
   }
 
@@ -407,7 +435,7 @@ class SmartTrimFormatter extends FormatterBase implements ContainerFactoryPlugin
           // Add space before each tag to ensure words don't run together.
           // Logic via https://stackoverflow.com/questions/12824899/strip-tags-replace-tags-by-space-rather-than-deleting-them
           $output = str_replace('<', ' <', $output);
-          $output = strip_tags($output);
+          $output = Xss::filter($output, $this->getSetting('trim_options_allowed_html'));
           $output = str_replace('  ', ' ', $output);
           $output = trim($output);