diff --git a/core/includes/common.inc b/core/includes/common.inc
index 54d4212..0ac62ca 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1338,9 +1338,9 @@ function l($text, $path, array $options = array()) {
   // The query parameters of an active link are equal to the current parameters.
   && ($variables['options']['query'] == $active['query']);
 
-  // Add the "active" class if appropriate.
+  // Add the "is-active" class if appropriate.
   if ($variables['url_is_active']) {
-    $variables['options']['attributes']['class'][] = 'active';
+    $variables['options']['attributes']['class'][] = 'is-active';
   }
 
   // Remove all HTML and PHP tags from a tooltip, calling expensive strip_tags()
diff --git a/core/includes/menu.inc b/core/includes/menu.inc
index 47e1103..fee0bb7 100644
--- a/core/includes/menu.inc
+++ b/core/includes/menu.inc
@@ -1156,7 +1156,7 @@ function menu_tree_output($tree) {
     // trees, so if the current path is a local task, and this link is its
     // tab root, then we have to set the class manually.
     if ($data['link']['href'] == $router_item['tab_root_href'] && $data['link']['href'] != current_path()) {
-      $data['link']['localized_options']['attributes']['class'][] = 'active';
+      $data['link']['localized_options']['attributes']['class'][] = 'is-active';
     }
 
     // Allow menu-specific theme overrides.
@@ -1766,7 +1766,7 @@ function theme_menu_local_task($variables) {
     $a_tag = \Drupal::l($link_text, $link['route_name'], $link['route_parameters'], $link['localized_options']);
   }
 
-  return '<li' . (!empty($variables['element']['#active']) ? ' class="active"' : '') . '>' . $a_tag . '</li>';
+  return '<li' . (!empty($variables['element']['#active']) ? ' class="is-active"' : '') . '>' . $a_tag . '</li>';
 }
 
 /**
@@ -1952,7 +1952,7 @@ function menu_navigation_links($menu_name, $level = 0) {
       // menu trees, so if the current path is a local task, and this link is
       // its tab root, then we have to set the class manually.
       if ($item['link']['href'] == $router_item['tab_root_href'] && $item['link']['href'] != current_path()) {
-        $l['attributes']['class'][] = 'active';
+        $l['attributes']['class'][] = 'is-active';
       }
       // Keyed with the unique mlid to generate classes in theme_links().
       $links['menu-' . $item['link']['mlid'] . $class] = $l;
@@ -2111,7 +2111,7 @@ function _menu_get_legacy_tasks($router_item, &$data, &$root_path) {
           // would not be marked as active, since l() only compares the href
           // with current_path().
           if ($link['href'] != current_path()) {
-            $link['localized_options']['attributes']['class'][] = 'active';
+            $link['localized_options']['attributes']['class'][] = 'is-active';
           }
           $tabs_current[$link['href']] = array(
             '#theme' => 'menu_local_task',
@@ -2189,7 +2189,7 @@ function _menu_get_legacy_tasks($router_item, &$data, &$root_path) {
           // links to its parent, l() will not mark it as active, as it only
           // compares the link's href to current_path().
           if ($link['href'] != current_path()) {
-            $link['localized_options']['attributes']['class'][] = 'active';
+            $link['localized_options']['attributes']['class'][] = 'is-active';
           }
           $tabs_current[$link['href']] = array(
             '#theme' => 'menu_local_task',
diff --git a/core/includes/tablesort.inc b/core/includes/tablesort.inc
index 1f6962b..3281074 100644
--- a/core/includes/tablesort.inc
+++ b/core/includes/tablesort.inc
@@ -49,7 +49,7 @@ function tablesort_header($cell, $header, $ts) {
       // http://www.w3.org/TR/wai-aria/states_and_properties#aria-sort
       $cell['aria-sort'] = ($ts['sort'] == 'asc') ? 'ascending' : 'descending';
       $ts['sort'] = (($ts['sort'] == 'asc') ? 'desc' : 'asc');
-      $cell['class'][] = 'active';
+      $cell['class'][] = 'is-active';
       $image = theme('tablesort_indicator', array('style' => $ts['sort']));
     }
     else {
@@ -84,10 +84,10 @@ function tablesort_header($cell, $header, $ts) {
 function tablesort_cell($cell, $header, $ts, $i) {
   if (isset($header[$i]['data']) && $header[$i]['data'] == $ts['name'] && !empty($header[$i]['field'])) {
     if (is_array($cell)) {
-      $cell['class'][] = 'active';
+      $cell['class'][] = 'is-active';
     }
     else {
-      $cell = array('data' => $cell, 'class' => array('active'));
+      $cell = array('data' => $cell, 'class' => array('is-active'));
     }
   }
   return $cell;
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 1d24dd5..3c5fe69 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1696,7 +1696,7 @@ function theme_links($variables) {
         $is_current_path = ($link['href'] == current_path() || ($link['href'] == '<front>' && drupal_is_front_page()));
         $is_current_language = (empty($link['language']) || $link['language']->id == $language_url->id);
         if ($is_current_path && $is_current_language) {
-          $class[] = 'active';
+          $class[] = 'is-active';
         }
         // @todo Reconcile Views usage of 'ajax' as a boolean with the rest of
         //   core's usage of it as an array.
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index b86a25d..d048624 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -132,7 +132,7 @@ function theme_task_list($variables) {
 
   foreach ($items as $k => $item) {
     if ($active == $k) {
-      $class = 'active';
+      $class = 'is-active';
       $status = '(' . t('active') . ')';
       $done = FALSE;
     }
diff --git a/core/modules/contextual/css/contextual.toolbar.css b/core/modules/contextual/css/contextual.toolbar.css
index 88442a4..3a36bad 100644
--- a/core/modules/contextual/css/contextual.toolbar.css
+++ b/core/modules/contextual/css/contextual.toolbar.css
@@ -22,7 +22,7 @@
 [dir="rtl"] .toolbar .toolbar-bar .contextual-toolbar-tab button {
   padding-right: 1.3333em;
 }
-.toolbar .toolbar-bar .contextual-toolbar-tab button.active {
+.toolbar .toolbar-bar .contextual-toolbar-tab button.is-active {
   background-image:-moz-linear-gradient(rgb(78,159,234) 0%,rgb(69,132,221) 100%);
   background-image:-webkit-gradient(linear,color-stop(0, rgb(78,159,234)),color-stop(1, rgb(69,132,221)));
   background-image: -webkit-linear-gradient(top,  rgb(78,159,234) 0%, rgb(69,132,221) 100%);
diff --git a/core/modules/contextual/js/contextual.toolbar.js b/core/modules/contextual/js/contextual.toolbar.js
index 53557e6..4a67c7f 100644
--- a/core/modules/contextual/js/contextual.toolbar.js
+++ b/core/modules/contextual/js/contextual.toolbar.js
@@ -151,7 +151,7 @@ Drupal.contextualToolbar = {
       // Render the visibility.
       this.$el.toggleClass('hidden', !this.model.get('isVisible'));
       // Render the state.
-      this.$el.find('button').toggleClass('active', !this.model.get('isViewing'));
+      this.$el.find('button').toggleClass('is-active', !this.model.get('isViewing'));
 
       return this;
     },
diff --git a/core/modules/dblog/css/dblog.module.css b/core/modules/dblog/css/dblog.module.css
index 9bfdda4..3f5a8e4 100644
--- a/core/modules/dblog/css/dblog.module.css
+++ b/core/modules/dblog/css/dblog.module.css
@@ -17,22 +17,22 @@
   padding: 3ex 0 0;
   vertical-align: top;
 }
-.dblog-user.odd .active {
+.dblog-user.odd .is-active {
   background: #ddf;
 }
-.dblog-user.even .active {
+.dblog-user.even .is-active {
   background: #cce;
 }
-.dblog-error.odd .active {
+.dblog-error.odd .is-active {
   background: #ffc9c9;
 }
-.dblog-error.even .active {
+.dblog-error.even .is-active {
   background: #eeb9b9;
 }
-.dblog-warning.odd .active {
+.dblog-warning.odd .is-active {
   background: #fffdca;
 }
-.dblog-warning.even .active {
+.dblog-warning.even .is-active {
   background: #eeedbd;
 }
 .admin-dblog .icon,
diff --git a/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php b/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php
index 8382590..174eb67 100644
--- a/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php
+++ b/core/modules/image/lib/Drupal/image/Tests/ImageFieldDisplayTest.php
@@ -111,7 +111,7 @@ function _testImageFieldFormatters($scheme) {
       '#width' => 40,
       '#height' => 20,
     );
-    $default_output = l($image, 'node/' . $nid, array('html' => TRUE, 'attributes' => array('class' => 'active')));
+    $default_output = l($image, 'node/' . $nid, array('html' => TRUE, 'attributes' => array('class' => 'is-active')));
     $this->drupalGet('node/' . $nid);
     $this->assertRaw($default_output, 'Image linked to content formatter displaying correctly on full node view.');
 
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
index 4613f43..a81caf3 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
@@ -62,32 +62,32 @@ function testLanguageBlock() {
     // Assert that only the current language is marked as active.
     list($language_switcher) = $this->xpath('//div[@id=:id]/div[contains(@class, "content")]', array(':id' => 'block-test-language-block'));
     $links = array(
-      'active' => array(),
+      'is-active' => array(),
       'inactive' => array(),
     );
     $anchors = array(
-      'active' => array(),
+      'is-active' => array(),
       'inactive' => array(),
     );
     foreach ($language_switcher->ul->li as $link) {
       $classes = explode(" ", (string) $link['class']);
       list($langcode) = array_intersect($classes, array('en', 'fr'));
-      if (in_array('active', $classes)) {
-        $links['active'][] = $langcode;
+      if (in_array('is-active', $classes)) {
+        $links['is-active'][] = $langcode;
       }
       else {
         $links['inactive'][] = $langcode;
       }
       $anchor_classes = explode(" ", (string) $link->a['class']);
-      if (in_array('active', $anchor_classes)) {
-        $anchors['active'][] = $langcode;
+      if (in_array('is-active', $anchor_classes)) {
+        $anchors['is-active'][] = $langcode;
       }
       else {
         $anchors['inactive'][] = $langcode;
       }
     }
-    $this->assertIdentical($links, array('active' => array('en'), 'inactive' => array('fr')), 'Only the current language list item is marked as active on the language switcher block.');
-    $this->assertIdentical($anchors, array('active' => array('en'), 'inactive' => array('fr')), 'Only the current language anchor is marked as active on the language switcher block.');
+    $this->assertIdentical($links, array('is-active' => array('en'), 'inactive' => array('fr')), 'Only the current language list item is marked as active on the language switcher block.');
+    $this->assertIdentical($anchors, array('is-active' => array('en'), 'inactive' => array('fr')), 'Only the current language anchor is marked as active on the language switcher block.');
   }
 
   /**
@@ -112,17 +112,17 @@ function testLanguageLinkActiveClass() {
 
     // Language code 'none' link should be active.
     $langcode = 'none';
-    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'active'));
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'is-active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
 
     // Language code 'en' link should be active.
     $langcode = 'en';
-    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'en_link', ':class' => 'active'));
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'en_link', ':class' => 'is-active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
 
     // Language code 'fr' link should not be active.
     $langcode = 'fr';
-    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'fr_link', ':class' => 'active'));
+    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'fr_link', ':class' => 'is-active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
 
     // Test links generated by l() on a French page.
@@ -131,17 +131,17 @@ function testLanguageLinkActiveClass() {
 
     // Language code 'none' link should be active.
     $langcode = 'none';
-    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'active'));
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'is-active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
 
     // Language code 'en' link should not be active.
     $langcode = 'en';
-    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'en_link', ':class' => 'active'));
+    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'en_link', ':class' => 'is-active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
 
     // Language code 'fr' link should be active.
     $langcode = 'fr';
-    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'fr_link', ':class' => 'active'));
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'fr_link', ':class' => 'is-active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
   }
 
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php
index 9bee36b..7b28f3f 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageUILanguageNegotiationTest.php
@@ -419,7 +419,7 @@ function testUrlLanguageFallback() {
     // Check that the language switcher active link matches the given browser
     // language.
     $args = array(':id' => 'block-test-language-block', ':url' => base_path() . $GLOBALS['script_path'] . $langcode_browser_fallback);
-    $fields = $this->xpath('//div[@id=:id]//a[@class="language-link active" and starts-with(@href, :url)]', $args);
+    $fields = $this->xpath('//div[@id=:id]//a[@class="language-link is-active" and starts-with(@href, :url)]', $args);
     $this->assertTrue($fields[0] == $languages[$langcode_browser_fallback]->name, 'The browser language is the URL active language');
 
     // Check that URLs are rewritten using the given browser language.
diff --git a/core/modules/overlay/css/overlay-child.css b/core/modules/overlay/css/overlay-child.css
index b40e3af..39069e1 100644
--- a/core/modules/overlay/css/overlay-child.css
+++ b/core/modules/overlay/css/overlay-child.css
@@ -127,10 +127,10 @@ html[dir="rtl"] {
   padding: 0 14px;
   text-decoration: none;
 }
-#overlay-tabs li.active a,
-#overlay-tabs li.active a.active,
-#overlay-tabs li.active a:active,
-#overlay-tabs li.active a:visited {
+#overlay-tabs li.is-active a,
+#overlay-tabs li.is-active a.is-active,
+#overlay-tabs li.is-active a:active,
+#overlay-tabs li.is-active a:visited {
   background-color: #fff;
   margin-bottom: 0;
   padding-bottom: 2px;
@@ -139,8 +139,8 @@ html[dir="rtl"] {
 #overlay-tabs li a:hover {
   color: #fff;
 }
-#overlay-tabs li.active a:focus,
-#overlay-tabs li.active a:hover {
+#overlay-tabs li.is-active a:focus,
+#overlay-tabs li.is-active a:hover {
   color: #000;
 }
 
diff --git a/core/modules/overlay/overlay-child.js b/core/modules/overlay/overlay-child.js
index cd7cdee..0fe2572 100644
--- a/core/modules/overlay/overlay-child.js
+++ b/core/modules/overlay/overlay-child.js
@@ -157,8 +157,8 @@ Drupal.overlayChild.behaviors.tabs = function (context, settings) {
 
   $('#overlay-tabs > li > a').bind('click.drupal-overlay', function () {
     var active_tab = Drupal.t('(active tab)');
-    $tabsLinks.parent().siblings().removeClass('active').find('visually-hidden:contains(' + active_tab + ')').appendTo(this);
-    $(this).parent().addClass('active');
+    $tabsLinks.parent().siblings().removeClass('is-active').find('visually-hidden:contains(' + active_tab + ')').appendTo(this);
+    $(this).parent().addClass('is-active');
   });
 };
 
diff --git a/core/modules/overlay/overlay-parent.js b/core/modules/overlay/overlay-parent.js
index ae1d5b8..3cc1df2 100644
--- a/core/modules/overlay/overlay-parent.js
+++ b/core/modules/overlay/overlay-parent.js
@@ -793,7 +793,7 @@ Drupal.overlay.resetActiveClass = function(activePath) {
   $('#toolbar-administration')
   .find('a[href]')
   // Remove active class from all links in displaced elements.
-  .removeClass('active')
+  .removeClass('is-active')
   // Add active class to links that match activePath.
   .each(function () {
     var linkDomain = this.protocol + this.hostname;
@@ -802,7 +802,7 @@ Drupal.overlay.resetActiveClass = function(activePath) {
     // A link matches if it is part of the active trail of activePath, except
     // for frontpage links.
     if (linkDomain === windowDomain && (activePath + '/').indexOf(linkPath + '/') === 0 && (linkPath !== '' || activePath === '')) {
-      $(this).addClass('active');
+      $(this).addClass('is-active');
     }
   });
 };
diff --git a/core/modules/system/css/system.theme.css b/core/modules/system/css/system.theme.css
index c6ed012..5a57f5b 100644
--- a/core/modules/system/css/system.theme.css
+++ b/core/modules/system/css/system.theme.css
@@ -16,10 +16,10 @@
 /**
  * Markup generated by theme_tablesort_indicator().
  */
-th.active img {
+th.is-active img {
   display: inline;
 }
-td.active {
+td.is-active {
   background-color: #ddd;
 }
 
@@ -392,7 +392,7 @@ ul.menu li {
   padding-top: 0.2em;
   margin: 0;
 }
-ul.menu a.active {
+ul.menu a.is-active {
   color: #000;
 }
 
@@ -458,7 +458,7 @@ ul.tabs {
   padding: 0.2em 1em;
   text-decoration: none;
 }
-.tabs a.active {
+.tabs a.is-active {
   background-color: #eee;
 }
 .tabs a:focus,
diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuTestBase.php
index d205b13..3ad683e 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuTestBase.php
@@ -119,7 +119,7 @@ protected function assertMenuActiveTrail($tree, $last_active) {
     $xpath .= 'li[contains(@class, :class-trail)]/a[contains(@href, :href) ' . $xpath_last_active . 'and contains(text(), :title)]';
     $args = array(
       ':class-trail' => 'active-trail',
-      ':class-active' => 'active',
+      ':class-active' => 'is-active',
       ':href' => url($active_link_path),
       ':title' => $active_link_title,
     );
diff --git a/core/modules/system/lib/Drupal/system/Tests/Pager/PagerTest.php b/core/modules/system/lib/Drupal/system/Tests/Pager/PagerTest.php
index dc8ead4..ba3997e 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Pager/PagerTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Pager/PagerTest.php
@@ -104,7 +104,7 @@ protected function assertPagerItems($current_page) {
         $this->assertNoClass($element, 'pager-current', "Item for page $page has no .pager-current class.");
         $this->assertClass($element, 'pager-item', "Item for page $page has .pager-item class.");
         $this->assertTrue($element->a, "Link to page $page found.");
-        $this->assertNoClass($element->a, 'active', "Link to page $page is not active.");
+        $this->assertNoClass($element->a, 'is-active', "Link to page $page is not active.");
       }
       unset($elements[--$page]);
     }
@@ -115,22 +115,22 @@ protected function assertPagerItems($current_page) {
     if (isset($first)) {
       $this->assertClass($first, 'pager-first', 'Item for first page has .pager-first class.');
       $this->assertTrue($first->a, 'Link to first page found.');
-      $this->assertNoClass($first->a, 'active', 'Link to first page is not active.');
+      $this->assertNoClass($first->a, 'is-active', 'Link to first page is not active.');
     }
     if (isset($previous)) {
       $this->assertClass($previous, 'pager-previous', 'Item for first page has .pager-previous class.');
       $this->assertTrue($previous->a, 'Link to previous page found.');
-      $this->assertNoClass($previous->a, 'active', 'Link to previous page is not active.');
+      $this->assertNoClass($previous->a, 'is-active', 'Link to previous page is not active.');
     }
     if (isset($next)) {
       $this->assertClass($next, 'pager-next', 'Item for next page has .pager-next class.');
       $this->assertTrue($next->a, 'Link to next page found.');
-      $this->assertNoClass($next->a, 'active', 'Link to next page is not active.');
+      $this->assertNoClass($next->a, 'is-active', 'Link to next page is not active.');
     }
     if (isset($last)) {
       $this->assertClass($last, 'pager-last', 'Item for last page has .pager-last class.');
       $this->assertTrue($last->a, 'Link to last page found.');
-      $this->assertNoClass($last->a, 'active', 'Link to last page is not active.');
+      $this->assertNoClass($last->a, 'is-active', 'Link to last page is not active.');
     }
   }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php
index 635883c..c77d57e8 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/FunctionsTest.php
@@ -164,7 +164,7 @@ function testLinks() {
     $expected_links .= '<ul id="somelinks">';
     $expected_links .= '<li class="a-link odd first"><a href="' . url('a/link') . '">' . check_plain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text even">' . check_plain('Plain "text"') . '</li>';
-    $expected_links .= '<li class="front-page odd last active"><a href="' . url('<front>') . '" class="active">' . check_plain('Front page') . '</a></li>';
+    $expected_links .= '<li class="front-page odd last is-active"><a href="' . url('<front>') . '" class="is-active">' . check_plain('Front page') . '</a></li>';
     $expected_links .= '</ul>';
 
     // Verify that passing a string as heading works.
@@ -196,7 +196,7 @@ function testLinks() {
     $expected_links .= '<ul id="somelinks">';
     $expected_links .= '<li class="a-link odd first"><a href="' . url('a/link') . '" class="a/class">' . check_plain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text even"><span class="a/class">' . check_plain('Plain "text"') . '</span></li>';
-    $expected_links .= '<li class="front-page odd last active"><a href="' . url('<front>') . '" class="active">' . check_plain('Front page') . '</a></li>';
+    $expected_links .= '<li class="front-page odd last is-active"><a href="' . url('<front>') . '" class="is-active">' . check_plain('Front page') . '</a></li>';
     $expected_links .= '</ul>';
     $expected = $expected_heading . $expected_links;
     $this->assertThemeOutput('links', $variables, $expected);
diff --git a/core/modules/toolbar/css/toolbar.icons.css b/core/modules/toolbar/css/toolbar.icons.css
index b10de97..1666b9e 100644
--- a/core/modules/toolbar/css/toolbar.icons.css
+++ b/core/modules/toolbar/css/toolbar.icons.css
@@ -72,11 +72,11 @@
   background-image: url("../../../misc/icons/bebebe/house.png");
 }
 .toolbar-bar .toolbar-icon-home:active:before,
-.toolbar-bar .toolbar-icon-home.active:before {
+.toolbar-bar .toolbar-icon-home.is-active:before {
   background-image: url("../../../misc/icons/ffffff/house.svg");
 }
 .no-svg .toolbar-bar .toolbar-icon-home:active:before,
-.no-svg .toolbar-bar .toolbar-icon-home.active:before {
+.no-svg .toolbar-bar .toolbar-icon-home.is-active:before {
   background-image: url("../../../misc/icons/ffffff/house.png");
 }
 .toolbar-bar .toolbar-icon-menu:before {
@@ -86,7 +86,7 @@
   background-image: url("../../../misc/icons/bebebe/hamburger.png");
 }
 .toolbar-bar .toolbar-icon-menu:active:before,
-.toolbar-bar .toolbar-icon-menu.active:before {
+.toolbar-bar .toolbar-icon-menu.is-active:before {
   background-image: url("../../../misc/icons/ffffff/hamburger.svg");
 }
 .no-svg .toolbar-bar .toolbar-icon-menu:active:before,
@@ -100,11 +100,11 @@
   background-image: url("../../../misc/icons/bebebe/questionmark-disc.png");
 }
 .toolbar-bar .toolbar-icon-help:active:before,
-.toolbar-bar .toolbar-icon-help.active:before {
+.toolbar-bar .toolbar-icon-help.is-active:before {
   background-image: url("../../../misc/icons/ffffff/questionmark-disc.svg");
 }
 .no-svg .toolbar-bar .toolbar-icon-help:active:before,
-.no-svg .toolbar-bar .toolbar-icon-help.active:before {
+.no-svg .toolbar-bar .toolbar-icon-help.is-active:before {
   background-image: url("../../../misc/icons/ffffff/questionmark-disc.png");
 }
 
@@ -118,11 +118,11 @@
   background-image: url("../../../misc/icons/787878/file.png");
 }
 .toolbar-icon-content:active:before,
-.toolbar-icon-content.active:before {
+.toolbar-icon-content.is-active:before {
   background-image: url("../../../misc/icons/000000/file.svg");
 }
 .no-svg .toolbar-icon-content:active:before,
-.no-svg .toolbar-icon-content.active:before {
+.no-svg .toolbar-icon-content.is-active:before {
   background-image: url("../../../misc/icons/000000/file.png");
 }
 .toolbar-icon-structure:before {
@@ -132,11 +132,11 @@
   background-image: url("../../../misc/icons/787878/orgchart.png");
 }
 .toolbar-icon-structure:active:before,
-.toolbar-icon-structure.active:before {
+.toolbar-icon-structure.is-active:before {
   background-image: url("../../../misc/icons/000000/orgchart.svg");
 }
 .no-svg .toolbar-icon-structure:active:before,
-.no-svg .toolbar-icon-structure.active:before {
+.no-svg .toolbar-icon-structure.is-active:before {
   background-image: url("../../../misc/icons/000000/orgchart.png");
 }
 .toolbar-icon-appearance:before {
@@ -146,11 +146,11 @@
   background-image: url("../../../misc/icons/787878/paintbrush.png");
 }
 .toolbar-icon-appearance:active:before,
-.toolbar-icon-appearance.active:before {
+.toolbar-icon-appearance.is-active:before {
   background-image: url("../../../misc/icons/000000/paintbrush.svg");
 }
 .no-svg .toolbar-icon-appearance:active:before,
-.no-svg .toolbar-icon-appearance.active:before {
+.no-svg .toolbar-icon-appearance.is-active:before {
   background-image: url("../../../misc/icons/000000/paintbrush.png");
 }
 .toolbar-icon-people:before {
@@ -160,11 +160,11 @@
   background-image: url("../../../misc/icons/787878/people.png");
 }
 .toolbar-icon-people:active:before,
-.toolbar-icon-people.active:before {
+.toolbar-icon-people.is-active:before {
   background-image: url("../../../misc/icons/000000/people.svg");
 }
 .no-svg .toolbar-icon-people:active:before,
-.no-svg .toolbar-icon-people.active:before {
+.no-svg .toolbar-icon-people.is-active:before {
   background-image: url("../../../misc/icons/000000/people.png");
 }
 .toolbar-icon-extend:before {
@@ -174,11 +174,11 @@
   background-image: url("../../../misc/icons/787878/puzzlepiece.png");
 }
 .toolbar-icon-extend:active:before,
-.toolbar-icon-extend.active:before {
+.toolbar-icon-extend.is-active:before {
   background-image: url("../../../misc/icons/000000/puzzlepiece.svg");
 }
 .no-svg .toolbar-icon-extend:active:before,
-.no-svg .toolbar-icon-extend.active:before {
+.no-svg .toolbar-icon-extend.is-active:before {
   background-image: url("../../../misc/icons/000000/puzzlepiece.png");
 }
 .toolbar-icon-configuration:before {
@@ -188,11 +188,11 @@
   background-image: url("../../../misc/icons/787878/wrench.png");
 }
 .toolbar-icon-configuration:active:before,
-.toolbar-icon-configuration.active:before {
+.toolbar-icon-configuration.is-active:before {
   background-image: url("../../../misc/icons/000000/wrench.svg");
 }
 .no-svg .toolbar-icon-configuration:active:before,
-.no-svg .toolbar-icon-configuration.active:before {
+.no-svg .toolbar-icon-configuration.is-active:before {
   background-image: url("../../../misc/icons/000000/wrench.png");
 }
 .toolbar-icon-reports:before {
@@ -202,11 +202,11 @@
   background-image: url("../../../misc/icons/787878/barchart.png");
 }
 .toolbar-icon-reports:active:before,
-.toolbar-icon-reports.active:before {
+.toolbar-icon-reports.is-active:before {
   background-image: url("../../../misc/icons/000000/barchart.svg");
 }
 .no-svg .toolbar-icon-reports:active:before,
-.no-svg .toolbar-icon-reports.active:before {
+.no-svg .toolbar-icon-reports.is-active:before {
   background-image: url("../../../misc/icons/000000/barchart.png");
 }
 .toolbar-icon-help:before {
@@ -216,11 +216,11 @@
   background-image: url("../../../misc/icons/787878/questionmark-disc.png");
 }
 .toolbar-icon-help:active:before,
-.toolbar-icon-help.active:before {
+.toolbar-icon-help.is-active:before {
   background-image: url("../../../misc/icons/000000/questionmark-disc.svg");
 }
 .no-svg .toolbar-icon-help:active:before,
-.no-svg .toolbar-icon-help.active:before {
+.no-svg .toolbar-icon-help.is-active:before {
   background-image: url("../../../misc/icons/000000/questionmark-disc.png");
 }
 
diff --git a/core/modules/toolbar/css/toolbar.menu.css b/core/modules/toolbar/css/toolbar.menu.css
index 8da6b37..d07f756 100644
--- a/core/modules/toolbar/css/toolbar.menu.css
+++ b/core/modules/toolbar/css/toolbar.menu.css
@@ -29,7 +29,7 @@
   margin-right: 0;
 }
 .toolbar .toolbar-tray .active-trail > .toolbar-box a,
-.toolbar .toolbar-tray a.active {
+.toolbar .toolbar-tray a.is-active {
   color: #000;
   font-weight: bold;
 }
diff --git a/core/modules/toolbar/css/toolbar.module.css b/core/modules/toolbar/css/toolbar.module.css
index 279d57b..679bf02 100644
--- a/core/modules/toolbar/css/toolbar.module.css
+++ b/core/modules/toolbar/css/toolbar.module.css
@@ -187,14 +187,14 @@ body.toolbar-fixed .toolbar .toolbar-tray-vertical {
   overflow-y: auto;
   position: fixed;
 }
-.toolbar .toolbar-tray.active {
+.toolbar .toolbar-tray.is-active {
   display: block;
 }
 /* Bring the tray into the viewport. By default it is just off-screen. */
-.toolbar-oriented .toolbar-tray-vertical.active {
+.toolbar-oriented .toolbar-tray-vertical.is-active {
   left: 0; /* LTR */
 }
-[dir="rtl"] .toolbar-oriented .toolbar-tray-vertical.active {
+[dir="rtl"] .toolbar-oriented .toolbar-tray-vertical.is-active {
   left: auto;
   right: 0;
 }
diff --git a/core/modules/toolbar/css/toolbar.theme.css b/core/modules/toolbar/css/toolbar.theme.css
index 5e2afe7..fc92a08 100644
--- a/core/modules/toolbar/css/toolbar.theme.css
+++ b/core/modules/toolbar/css/toolbar.theme.css
@@ -45,7 +45,7 @@
   background-image: linear-gradient(rgba(255, 255, 255, 0.125) 20%, transparent 200%);
   text-decoration: none;
 }
-.toolbar .toolbar-bar .toolbar-tab > a.active {
+.toolbar .toolbar-bar .toolbar-tab > a.is-active {
   background-image: -webkit-linear-gradient(rgba(255, 255, 255, 0.25) 20%, transparent 200%);
   background-image: linear-gradient(rgba(255, 255, 255, 0.25) 20%, transparent 200%);
 }
@@ -88,7 +88,7 @@
 }
 .toolbar .toolbar-tray a:hover,
 .toolbar .toolbar-tray a:active,
-.toolbar .toolbar-tray a.active {
+.toolbar .toolbar-tray a.is-active {
   color: #000;
 }
 .toolbar .toolbar-tray-horizontal .menu {
diff --git a/core/modules/toolbar/js/toolbar.js b/core/modules/toolbar/js/toolbar.js
index d94fde6..5208522 100644
--- a/core/modules/toolbar/js/toolbar.js
+++ b/core/modules/toolbar/js/toolbar.js
@@ -502,9 +502,9 @@ Drupal.toolbar = {
       // Remove data-offset attributes from the trays so they can be refreshed.
       $trays.removeAttr('data-offset-left data-offset-right data-offset-top');
       // If an active vertical tray exists, mark it as an offset element.
-      $trays.filter('.toolbar-tray-vertical.active').attr('data-offset-' + edge, '');
+      $trays.filter('.toolbar-tray-vertical.is-active').attr('data-offset-' + edge, '');
       // If an active horizontal tray exists, mark it as an offset element.
-      $trays.filter('.toolbar-tray-horizontal.active').attr('data-offset-top', '');
+      $trays.filter('.toolbar-tray-horizontal.is-active').attr('data-offset-top', '');
     },
 
     /**
diff --git a/core/modules/toolbar/js/toolbar.menu.js b/core/modules/toolbar/js/toolbar.menu.js
index e440f23..f5cd341 100644
--- a/core/modules/toolbar/js/toolbar.menu.js
+++ b/core/modules/toolbar/js/toolbar.menu.js
@@ -123,7 +123,7 @@ var activeItem = drupalSettings.basePath + Drupal.encodePath(drupalSettings.curr
         activeItem = location.pathname;
       }
       if (activeItem) {
-        var $activeItem = $menu.find('a[href="' + activeItem + '"]').addClass('active');
+        var $activeItem = $menu.find('a[href="' + activeItem + '"]').addClass('is-active');
         var $activeTrail = $activeItem.parentsUntil('.root', 'li').addClass('active-trail');
         toggleList($activeTrail, true);
       }
diff --git a/core/modules/tour/css/tour.module.css b/core/modules/tour/css/tour.module.css
index afb0afd..a8d875a 100644
--- a/core/modules/tour/css/tour.module.css
+++ b/core/modules/tour/css/tour.module.css
@@ -16,7 +16,7 @@
   color: #fff;
   font-weight: bold;
 }
-.toolbar .tour-toolbar-tab button.active {
+.toolbar .tour-toolbar-tab button.is-active {
   background-image: -webkit-linear-gradient(rgba(255, 255, 255, 0.25) 20%, transparent 200%);
   background-image: linear-gradient(rgba(255, 255, 255, 0.25) 20%, transparent 200%);
 }
diff --git a/core/modules/tour/js/tour.js b/core/modules/tour/js/tour.js
index 86357e7..ddb9573 100644
--- a/core/modules/tour/js/tour.js
+++ b/core/modules/tour/js/tour.js
@@ -117,7 +117,7 @@ Drupal.tour.views.ToggleTourView = Backbone.View.extend({
     // Render the state.
     var isActive = this.model.get('isActive');
     this.$el.find('button')
-      .toggleClass('active', isActive)
+      .toggleClass('is-active', isActive)
       .prop('aria-pressed', isActive);
     return this;
   },
diff --git a/core/modules/user/css/user.module.css b/core/modules/user/css/user.module.css
index f96703e..248579a 100644
--- a/core/modules/user/css/user.module.css
+++ b/core/modules/user/css/user.module.css
@@ -109,4 +109,4 @@ div.password-suggestions ul {
     width: 100%;
     max-width: none;
   }
-}
+}
\ No newline at end of file
diff --git a/core/modules/views/lib/Drupal/views/Tests/Plugin/DisplayPageWebTest.php b/core/modules/views/lib/Drupal/views/Tests/Plugin/DisplayPageWebTest.php
index 4ea268a..7ac9206 100644
--- a/core/modules/views/lib/Drupal/views/Tests/Plugin/DisplayPageWebTest.php
+++ b/core/modules/views/lib/Drupal/views/Tests/Plugin/DisplayPageWebTest.php
@@ -77,7 +77,7 @@ public function testPageDisplayMenu() {
     $this->assertResponse(200);
     $element = $this->xpath('//ul[contains(@class, :ul_class)]//a[contains(@class, :a_class)]', array(
       ':ul_class' => 'tabs primary',
-      ':a_class' => 'active',
+      ':a_class' => 'is-active',
     ));
     $this->assertEqual((string) $element[0], t('Test default tab'));
     $this->assertTitle(t('Test default page | Drupal'));
@@ -89,7 +89,7 @@ public function testPageDisplayMenu() {
     $this->assertResponse(200);
     $element = $this->xpath('//ul[contains(@class, :ul_class)]//a[contains(@class, :a_class)]', array(
       ':ul_class' => 'tabs primary',
-      ':a_class' => 'active',
+      ':a_class' => 'is-active',
     ));
     $this->assertEqual((string) $element[0], t('Test local tab'));
     $this->assertTitle(t('Test local page | Drupal'));
diff --git a/core/modules/views/views.theme.inc b/core/modules/views/views.theme.inc
index 65f8ac4..d26a831 100644
--- a/core/modules/views/views.theme.inc
+++ b/core/modules/views/views.theme.inc
@@ -414,7 +414,7 @@ function template_preprocess_views_view_summary(&$variables) {
     $variables['rows'][$id]->url = url($view->getUrl($args, $base_path), $url_options);
     $variables['rows'][$id]->count = intval($row->{$argument->count_alias});
     if (isset($active_urls[$variables['rows'][$id]->url])) {
-      $variables['rows'][$id]->attributes['class'][] = 'active';
+      $variables['rows'][$id]->attributes['class'][] = 'is-active';
     }
     $variables['rows'][$id]->attributes = new Attribute($variables['rows'][$id]->attributes);
   }
@@ -477,7 +477,7 @@ function template_preprocess_views_view_summary_unformatted(&$variables) {
     $variables['rows'][$id]->url = url($view->getUrl($args, $base_path), $url_options);
     $variables['rows'][$id]->count = intval($row->{$argument->count_alias});
     if (isset($active_urls[$variables['rows'][$id]->url])) {
-      $variables['rows'][$id]->attributes['class'][] = 'active';
+      $variables['rows'][$id]->attributes['class'][] = 'is-active';
     }
     $variables['rows'][$id]->attributes = new Attribute($variables['rows'][$id]->attributes);
   }
@@ -532,7 +532,7 @@ function template_preprocess_views_view_table(&$variables) {
     // what the CSS classes should be.
     $variables['fields'][$field] = drupal_clean_css_identifier($field);
     if ($active == $field) {
-      $variables['fields'][$field] .= ' active';
+      $variables['fields'][$field] .= ' is-active';
     }
 
     // Render the header labels.
diff --git a/core/modules/views_ui/config/tour.tour.views-ui.yml b/core/modules/views_ui/config/tour.tour.views-ui.yml
index a7e6fa9..88af889 100644
--- a/core/modules/views_ui/config/tour.tour.views-ui.yml
+++ b/core/modules/views_ui/config/tour.tour.views-ui.yml
@@ -13,7 +13,7 @@ tips:
     body: 'This is the active display in the view. When there are multiple displays, one link for each display is shown and you can switch displays simply by clicking on the display link.'
     weight: 2
     attributes:
-      data-class: 'views-display-top li.active'
+      data-class: 'views-display-top li.is-active'
   views-ui-displays:
     id: views-ui-displays
     plugin: text
diff --git a/core/modules/views_ui/css/views_ui.admin.theme.css b/core/modules/views_ui/css/views_ui.admin.theme.css
index 9a71196..1b9cfed 100644
--- a/core/modules/views_ui/css/views_ui.admin.theme.css
+++ b/core/modules/views_ui/css/views_ui.admin.theme.css
@@ -471,7 +471,7 @@ ul#views-display-menu-tabs li.add ul.action-list li{
 /**
  * Display a red border if the display doesn't validate.
  */
-.views-displays ul.secondary li.active a.active.error,
+.views-displays ul.secondary li.is-active a.is-active.error,
 .views-displays .secondary a.error {
   border: 2px solid #ed541d;
   padding: 1px 6px;
@@ -486,8 +486,8 @@ ul#views-display-menu-tabs li.add ul.action-list li{
 }
 
 .views-displays ul.secondary li a:hover,
-.views-displays ul.secondary li.active a,
-.views-displays ul.secondary li.active a.active {
+.views-displays ul.secondary li.is-active a,
+.views-displays ul.secondary li.is-active a.is-active {
   background-color: #555;
   color: #fff;
 }
diff --git a/core/themes/bartik/color/preview.css b/core/themes/bartik/color/preview.css
index 65e9ad7..10b6022 100644
--- a/core/themes/bartik/color/preview.css
+++ b/core/themes/bartik/color/preview.css
@@ -59,7 +59,7 @@
   background: #b3b3b3;
   background: rgba(255, 255, 255, 1);
 }
-#preview-main-menu-links li a.active {
+#preview-main-menu-links li a.is-active {
   border-bottom: none;
 }
 #preview-main-menu-links li {
diff --git a/core/themes/bartik/css/colors.css b/core/themes/bartik/css/colors.css
index 96f3877..0ab991f 100644
--- a/core/themes/bartik/css/colors.css
+++ b/core/themes/bartik/css/colors.css
@@ -9,14 +9,14 @@ body.overlay {
 }
 #page,
 #main-wrapper,
-#main-menu-links li a.active,
-#main-menu-links li.active-trail a {
+#main-menu-links li a.is-active,
+#main-menu-links li.is-active-trail a {
   background: #ffffff;
 }
-.tabs ul.primary li a.active {
+.tabs ul.primary li a.is-active {
   background-color: #ffffff;
 }
-.tabs ul.primary li.active a {
+.tabs ul.primary li.is-active a {
   background-color: #ffffff;
   border-bottom: 1px solid #ffffff;
 }
@@ -53,7 +53,7 @@ a:active,
 }
 .region-header,
 .region-header a,
-.region-header li a.active,
+.region-header li a.is-active,
 #name-and-slogan,
 #name-and-slogan a,
 #secondary-menu-links li a {
diff --git a/core/themes/bartik/css/style.css b/core/themes/bartik/css/style.css
index 5dad110..c64d0e5 100644
--- a/core/themes/bartik/css/style.css
+++ b/core/themes/bartik/css/style.css
@@ -572,7 +572,7 @@ h1#site-name {
   background: #b3b3b3;
   background: rgba(255, 255, 255, 1);
 }
-#main-menu-links li a.active {
+#main-menu-links li a.is-active {
   border-bottom: none;
 }
 
@@ -1124,7 +1124,7 @@ div.tabs {
   float: right;
   zoom: 1;
 }
-.tabs ul.primary li.active a {
+.tabs ul.primary li.is-active a {
   border-bottom: 1px solid #ffffff;
 }
 .tabs ul.primary li a {
@@ -1144,7 +1144,7 @@ div.tabs {
   border-top-left-radius: 6px;
   border-top-right-radius: 6px;
 }
-.tabs ul.primary li.active a {
+.tabs ul.primary li.is-active a {
   background-color: #ffffff;
   border: 1px solid #bbb;
   border-bottom: 1px solid #fff;
@@ -1183,7 +1183,7 @@ div.tabs {
   padding: 0.25em 0.5em;
   text-decoration: none;
 }
-.tabs ul.secondary li a.active {
+.tabs ul.secondary li a.is-active {
   background: #f2f2f2;
   border-bottom: none;
   border-radius: 5px;
@@ -1891,7 +1891,7 @@ div.admin-panel .description {
     padding: 0.7em 0.8em;
   }
   .featured #main-menu-links li a:active,
-  .featured #main-menu-links li a.active {
+  .featured #main-menu-links li a.is-active {
     background: #f0f0f0;
     background: rgba(240, 240, 240, 1.0);
   }
diff --git a/core/themes/seven/install-page.css b/core/themes/seven/install-page.css
index 0d223f0..6e390bf 100644
--- a/core/themes/seven/install-page.css
+++ b/core/themes/seven/install-page.css
@@ -119,12 +119,12 @@ body.install-page #page-title {
 [dir="rtl"] .install-task-list li {
   padding: 0.5em 20px 0.5em 1em;
 }
-.install-task-list li.active {
+.install-task-list li.is-active {
   background: #ebeae4;
   position: relative;
   font-weight: normal;
 }
-.install-task-list li.active:after {
+.install-task-list li.is-active:after {
   left: 100%; /* LTR */
   border: solid transparent;
   border-color: rgba(235, 234, 228, 0);
@@ -138,7 +138,7 @@ body.install-page #page-title {
   top: 50%;
   margin-top: -17px;
 }
-[dir="rtl"] .install-task-list li.active:after {
+[dir="rtl"] .install-task-list li.is-active:after {
   left: auto;
   right: 100%;
   border-left-color: transparent;
diff --git a/core/themes/seven/js/mobile.install.js b/core/themes/seven/js/mobile.install.js
index 6ee8934..3083f58 100644
--- a/core/themes/seven/js/mobile.install.js
+++ b/core/themes/seven/js/mobile.install.js
@@ -4,7 +4,7 @@
 
   function findActiveStep (steps) {
     for (var i = 0; i < steps.length; i++) {
-      if (steps[i].className === 'active') {
+      if (steps[i].className === 'is-active') {
         return i + 1;
       }
     }
diff --git a/core/themes/seven/style.css b/core/themes/seven/style.css
index 5866808..8b8b383 100644
--- a/core/themes/seven/style.css
+++ b/core/themes/seven/style.css
@@ -276,11 +276,11 @@ ul.primary li {
   float: right;
 }
 ul.primary li a:link,
-ul.primary li a.active,
+ul.primary li a.is-active,
 ul.primary li a:active,
 ul.primary li a:visited,
 ul.primary li a:hover,
-ul.primary li.active a {
+ul.primary li.is-active a {
   display: block;
   float: left; /* LTR */
   padding: 0.615em 18px;
@@ -293,24 +293,24 @@ ul.primary li.active a {
   border-radius: 8px 8px 0 0;
 }
 [dir="rtl"] ul.primary li a:link,
-[dir="rtl"] ul.primary li a.active,
+[dir="rtl"] ul.primary li a.is-active,
 [dir="rtl"] ul.primary li a:active,
 [dir="rtl"] ul.primary li a:visited,
 [dir="rtl"] ul.primary li a:hover,
-[dir="rtl"] ul.primary li.active a {
+[dir="rtl"] ul.primary li.is-active a {
   float: right;
 }
-ul.primary li.active a,
-ul.primary li.active a.active,
-ul.primary li.active a:active,
-ul.primary li.active a:visited {
+ul.primary li.is-active a,
+ul.primary li.is-active a.is-active,
+ul.primary li.is-active a:active,
+ul.primary li.is-active a:visited {
   background-color: #fff;
   border-color: #c9cac4;
 }
 ul.primary li a:hover {
   color: #fff;
 }
-ul.primary li.active a:hover {
+ul.primary li.is-active a:hover {
   color: #000;
 }
 .tabs-secondary {
@@ -341,14 +341,14 @@ ul.secondary li a {
 }
 ul.secondary li a,
 ul.secondary li a:hover,
-ul.secondary li.active a,
-ul.secondary li.active a.active {
+ul.secondary li.is-active a,
+ul.secondary li.is-active a.is-active {
   padding: 2px 10px;
   border-radius: 7px;
 }
 ul.secondary li a:hover,
-ul.secondary li.active a,
-ul.secondary li.active a.active {
+ul.secondary li.is-active a,
+ul.secondary li.is-active a.is-active {
   color: #fff;
   background: #666;
 }
@@ -389,11 +389,11 @@ ul.secondary li.active a.active {
     white-space: nowrap;
   }
   .touch ul.primary li a:link,
-  .touch ul.primary li a.active,
+  .touch ul.primary li a.is-active,
   .touch ul.primary li a:active,
   .touch ul.primary li a:visited,
   .touch ul.primary li a:hover,
-  .touch ul.primary li.active a {
+  .touch ul.primary li.is-active a {
     -webkit-box-sizing: border-box;
     -moz-box-sizing: border-box;
     box-sizing: border-box;
@@ -590,7 +590,6 @@ th > a {
   color: #0074bd;
   text-decoration: none;
 }
-
 /* 1. Must match negative bottom padding of the parent <th> */
 th > a:after {
   content: '';
@@ -603,15 +602,15 @@ th > a:after {
   border-bottom: 2px solid transparent;
   transition: all 0.1s;
 }
-th.active > a {
+th.is-active > a {
   color: #004875;
 }
-th.active img {
+th.is-active img {
   position: absolute;
   right: 0; /* LTR */
   top: 50%;
 }
-[dir="rtl"] th.active img {
+[dir="rtl"] th.is-active img {
   right: auto;
   left: 0;
 }
@@ -620,21 +619,21 @@ th.active > a:after {
 }
 th > a:focus,
 th > a:hover,
-th.active > a:focus,
-th.active > a:hover {
+th.is-active > a:focus,
+th.is-active > a:hover {
   color: #008ee6;
   text-decoration: none;
 }
 th > a:focus:after,
 th > a:hover:after,
-th.active > a:focus:after,
-th.active > a:hover:after {
+th.is-active > a:focus:after,
+th.is-active > a:hover:after {
   border-bottom-color: #008ee6;
 }
 td .item-list ul {
   margin: 0;
 }
-td.active {
+td.is-active {
   background: none;
 }
 
@@ -1151,12 +1150,12 @@ body.in-maintenance #logo {
 [dir="rtl"] .task-list li {
   padding: 0.5em 20px 0.5em 1em;
 }
-.task-list li.active {
+.task-list li.is-active {
   background: transparent url(images/task-item.png) no-repeat 3px 50%; /* LTR */
   padding: 0.5em 1em 0.5em 20px; /* LTR */
   color: #000;
 }
-[dir="rtl"] .task-list li.active {
+[dir="rtl"] .task-list li.is-active {
   background: transparent url(images/task-item-rtl.png) no-repeat right 50%;
   padding: 0.5em 20px 0.5em 1em;
 }
@@ -1450,8 +1449,8 @@ details.fieldset-no-legend {
 }
 
 .views-displays ul.secondary li a,
-.views-displays ul.secondary li.active a,
-.views-displays ul.secondary li.active a.active {
+.views-displays ul.secondary li.is-active a,
+.views-displays ul.secondary li.is-active a.is-active {
   padding: 2px 7px 3px;
 }
 
@@ -1459,8 +1458,8 @@ details.fieldset-no-legend {
   color: #0074bd;
 }
 
-.views-displays ul.secondary li.active a,
-.views-displays ul.secondary li.active a.active {
+.views-displays ul.secondary li.is-active a,
+.views-displays ul.secondary li.is-active a.is-active {
   border: 1px solid transparent;
 }