diff --git a/core/modules/filter/src/Tests/FilterUnitTest.php b/core/modules/filter/src/Tests/FilterUnitTest.php
index 3e87393..2c2a5c9 100644
--- a/core/modules/filter/src/Tests/FilterUnitTest.php
+++ b/core/modules/filter/src/Tests/FilterUnitTest.php
@@ -118,7 +118,7 @@ function testCaptionFilter() {
 
     // Data-caption attribute.
     $input = '<img src="llama.jpg" data-caption="Loquacious llama!" />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
@@ -130,14 +130,14 @@ function testCaptionFilter() {
 
     // HTML entities in the caption.
     $input = '<img src="llama.jpg" data-caption="&ldquo;Loquacious llama!&rdquo;" />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption>“Loquacious llama!”</figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption>“Loquacious llama!”</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
 
     // HTML encoded as HTML entities in data-caption attribute.
     $input = '<img src="llama.jpg" data-caption="&lt;em&gt;Loquacious llama!&lt;/em&gt;" />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption><em>Loquacious llama!</em></figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption><em>Loquacious llama!</em></figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
@@ -146,33 +146,33 @@ function testCaptionFilter() {
     // not allowed by the HTML spec, but may happen when people manually write
     // HTML, so we explicitly support it.
     $input = '<img src="llama.jpg" data-caption="<em>Loquacious llama!</em>" />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption><em>Loquacious llama!</em></figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption><em>Loquacious llama!</em></figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
 
     // Security test: attempt an XSS.
     $input = '<img src="llama.jpg" data-caption="<script>alert(\'Loquacious llama!\')</script>" />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption>alert(\'Loquacious llama!\')</figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption>alert(\'Loquacious llama!\')</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
 
     // Ensure the filter also works with uncommon yet valid attribute quoting.
     $input = '<img src=llama.jpg data-caption=\'Loquacious llama!\' />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
 
     // Finally, ensure that this also works on any other tag.
     $input = '<video src="llama.jpg" data-caption="Loquacious llama!" />';
-    $expected = '<figure class="caption caption-video"><video src="llama.jpg"></video><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure><video src="llama.jpg"></video><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
     $input = '<foobar data-caption="Loquacious llama!">baz</foobar>';
-    $expected = '<figure class="caption caption-foobar"><foobar>baz</foobar><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure><foobar>baz</foobar><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
@@ -198,17 +198,17 @@ function testAlignAndCaptionFilters() {
     // Both data-caption and data-align attributes: all 3 allowed values for the
     // data-align attribute.
     $input = '<img src="llama.jpg" data-caption="Loquacious llama!" data-align="left" />';
-    $expected = '<figure class="caption caption-img align-left"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure class="align-left"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
     $input = '<img src="llama.jpg" data-caption="Loquacious llama!" data-align="center" />';
-    $expected = '<figure class="caption caption-img align-center"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure class="align-center"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
     $input = '<img src="llama.jpg" data-caption="Loquacious llama!" data-align="right" />';
-    $expected = '<figure class="caption caption-img align-right"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure class="align-right"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
@@ -216,7 +216,7 @@ function testAlignAndCaptionFilters() {
     // Both data-caption and data-align attributes, but a disallowed data-align
     // attribute value.
     $input = '<img src="llama.jpg" data-caption="Loquacious llama!" data-align="left foobar" />';
-    $expected = '<figure class="caption caption-img"><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
+    $expected = '<figure><img src="llama.jpg" /><figcaption>Loquacious llama!</figcaption></figure>';
     $output = $test($input);
     $this->assertIdentical($expected, $output->getProcessedText());
     $this->assertIdentical($attached_library, $output->getAssets());
diff --git a/core/modules/filter/src/Tests/TextFormatElementFormTest.php b/core/modules/filter/src/Tests/TextFormatElementFormTest.php
index f2d682b..b889c4a 100644
--- a/core/modules/filter/src/Tests/TextFormatElementFormTest.php
+++ b/core/modules/filter/src/Tests/TextFormatElementFormTest.php
@@ -117,9 +117,9 @@ public function testTextFormatElement() {
     $output = $this->render($form);
     $this->setRawContent($output);
     $this->assertFieldByName('textformat[value]');
-    $this->assertRaw('<h4 class="label">Full HTML</h4>');
-    $this->assertRaw('<h4 class="label">Filtered HTML</h4>');
-    $this->assertRaw('<h4 class="label">Test format</h4>');
+    $this->assertRaw('<h4>Full HTML</h4>');
+    $this->assertRaw('<h4>Filtered HTML</h4>');
+    $this->assertRaw('<h4>Test format</h4>');
     $this->assertNoPattern('|<h4[^>]*></h4>|', 'No empty H4 element found.');
   }
 
diff --git a/core/modules/filter/templates/filter-caption.html.twig b/core/modules/filter/templates/filter-caption.html.twig
index eb9d248..f015ac0 100644
--- a/core/modules/filter/templates/filter-caption.html.twig
+++ b/core/modules/filter/templates/filter-caption.html.twig
@@ -12,7 +12,7 @@
  * - string classes: The classes of the captioned HTML tag.
  */
 #}
-<figure class="caption caption-{{ tag }}{%- if classes %} {{ classes }}{%- endif %}">
+<figure{%- if classes %} class="{{ classes }}"{%- endif %}>
 {{ node }}
 <figcaption>{{ caption }}</figcaption>
 </figure>
diff --git a/core/modules/filter/templates/filter-guidelines.html.twig b/core/modules/filter/templates/filter-guidelines.html.twig
index 783992b..317cfa6 100644
--- a/core/modules/filter/templates/filter-guidelines.html.twig
+++ b/core/modules/filter/templates/filter-guidelines.html.twig
@@ -19,13 +19,7 @@
  * @ingroup themeable
  */
 #}
-{%
-  set classes = [
-    'filter-guidelines-item',
-    'filter-guidelines-' ~ format.format,
-  ]
-%}
-<div{{ attributes.addClass(classes) }}>
-  <h4 class="label">{{ format.label }}</h4>
+<div{{ attributes }}>
+  <h4>{{ format.label }}</h4>
   {{ tips }}
 </div>
diff --git a/core/modules/filter/templates/filter-tips.html.twig b/core/modules/filter/templates/filter-tips.html.twig
index b17de01..b020c23 100644
--- a/core/modules/filter/templates/filter-tips.html.twig
+++ b/core/modules/filter/templates/filter-tips.html.twig
@@ -24,30 +24,19 @@
 
 {% if tips|length %}
   {% if multiple %}
-    <div class="compose-tips">
+    <div>
   {% endif %}
 
   {% for name, tip in tips %}
     {% if multiple %}
-      {%
-        set tip_classes = [
-          'filter-type',
-          'filter-' ~ name|clean_class,
-        ]
-      %}
-      <div{{ tip.attributes.addClass(tip_classes) }}>
+      <div{{ attributes }}>
       <h3>{{ tip.name }}</h3>
     {% endif %}
 
     {% if tip.list|length %}
-      <ul class="tips">
+      <ul>
       {% for item in tip.list %}
-        {%
-          set item_classes = [
-            long ? 'filter-' ~ item.id|replace({'/': '-'}),
-          ]
-        %}
-        <li{{ item.attributes.addClass(item_classes) }}>{{ item.tip }}</li>
+        <li{{ tip.attributes }}>{{ item.tip }}</li>
       {% endfor %}
       </ul>
     {% endif %}
diff --git a/core/modules/filter/templates/text-format-wrapper.html.twig b/core/modules/filter/templates/text-format-wrapper.html.twig
index 4e5ff6d..ce3ba55 100644
--- a/core/modules/filter/templates/text-format-wrapper.html.twig
+++ b/core/modules/filter/templates/text-format-wrapper.html.twig
@@ -15,14 +15,9 @@
  * @ingroup themeable
  */
 #}
-<div class="text-format-wrapper form-item">
+<div>
   {{ children }}
   {% if description %}
-    {%
-      set classes = [
-        aria_description ? 'description',
-      ]
-    %}
-    <div{{ attributes.addClass(classes) }}>{{ description }}</div>
+    <div{{ attributes }}>{{ description }}</div>
   {% endif %}
 </div>
diff --git a/core/modules/filter/templates/filter-caption.html.twig b/core/themes/classy/templates/filter-caption.html.twig
similarity index 100%
copy from core/modules/filter/templates/filter-caption.html.twig
copy to core/themes/classy/templates/filter-caption.html.twig
diff --git a/core/modules/filter/templates/filter-guidelines.html.twig b/core/themes/classy/templates/filter-guidelines.html.twig
similarity index 100%
copy from core/modules/filter/templates/filter-guidelines.html.twig
copy to core/themes/classy/templates/filter-guidelines.html.twig
diff --git a/core/modules/filter/templates/filter-tips.html.twig b/core/themes/classy/templates/filter-tips.html.twig
similarity index 100%
copy from core/modules/filter/templates/filter-tips.html.twig
copy to core/themes/classy/templates/filter-tips.html.twig
diff --git a/core/modules/filter/templates/text-format-wrapper.html.twig b/core/themes/classy/templates/text-format-wrapper.html.twig
similarity index 100%
copy from core/modules/filter/templates/text-format-wrapper.html.twig
copy to core/themes/classy/templates/text-format-wrapper.html.twig