diff --git a/core/core.libraries.yml b/core/core.libraries.yml
index 7698576..48ecfe4 100644
--- a/core/core.libraries.yml
+++ b/core/core.libraries.yml
@@ -185,11 +185,11 @@ drupal.dialog.ajax:
 drupal.dialog.off_canvas:
   version: VERSION
   js:
-    misc/dialog/offcanvas.js: {}
+    misc/dialog/off-canvas.js: {}
   css:
     component:
-      misc/dialog/offcanvas.css: {}
-      misc/dialog/offcanvas.motion.css: {}
+      misc/dialog/off-canvas.css: {}
+      misc/dialog/off-canvas.motion.css: {}
   dependencies:
     - core/jquery
     - core/drupal
diff --git a/core/core.services.yml b/core/core.services.yml
index f8b1522..a7b1654 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1063,7 +1063,7 @@ services:
     class: Drupal\Core\Render\MainContent\OffCanvasRender
     arguments: ['@title_resolver', '@renderer']
     tags:
-      - { name: render.main_content_renderer, format: drupal_dialog.offcanvas }
+      - { name: render.main_content_renderer, format: drupal_dialog.off_canvas }
   main_content_renderer.modal:
     class: Drupal\Core\Render\MainContent\ModalRenderer
     arguments: ['@title_resolver']
diff --git a/core/lib/Drupal/Core/Ajax/OpenOffCanvasDialogCommand.php b/core/lib/Drupal/Core/Ajax/OpenOffCanvasDialogCommand.php
index fbb4761..96ad51c 100644
--- a/core/lib/Drupal/Core/Ajax/OpenOffCanvasDialogCommand.php
+++ b/core/lib/Drupal/Core/Ajax/OpenOffCanvasDialogCommand.php
@@ -31,7 +31,7 @@ class OpenOffCanvasDialogCommand extends OpenDialogCommand {
    *   populated automatically from the current request.
    */
   public function __construct($title, $content, array $dialog_options = [], $settings = NULL) {
-    parent::__construct('#drupal-offcanvas', $title, $content, $dialog_options, $settings);
+    parent::__construct('#drupal-off-canvas', $title, $content, $dialog_options, $settings);
     $this->dialogOptions['modal'] = FALSE;
     $this->dialogOptions['autoResize'] = FALSE;
     $this->dialogOptions['resizable'] = 'w';
diff --git a/core/lib/Drupal/Core/Render/MainContent/OffCanvasRender.php b/core/lib/Drupal/Core/Render/MainContent/OffCanvasRender.php
index 0729d3b..c1eeaab 100644
--- a/core/lib/Drupal/Core/Render/MainContent/OffCanvasRender.php
+++ b/core/lib/Drupal/Core/Render/MainContent/OffCanvasRender.php
@@ -10,7 +10,7 @@
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * Default main content renderer for offcanvas dialog requests.
+ * Default main content renderer for off_canvas dialog requests.
  */
 class OffCanvasRender extends DialogRenderer {
 
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index fa32e05..524e978 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -314,7 +314,7 @@
    * @prop {string} [dialogType]
    *   One of `'modal'` or `'dialog'`.
    * @prop {string} [drupalDialogRenderer]
-   *   Renderer for the dialog, 'offcanvas' supported.
+   *   Renderer for the dialog, 'off_canvas' supported.
    * @prop {string} [prevent]
    *   List of events on which to stop default action and stop propagation.
    */
diff --git a/core/misc/dialog/offcanvas.css b/core/misc/dialog/off-canvas.css
similarity index 64%
rename from core/misc/dialog/offcanvas.css
rename to core/misc/dialog/off-canvas.css
index 0e46c6a..170e962 100644
--- a/core/misc/dialog/offcanvas.css
+++ b/core/misc/dialog/off-canvas.css
@@ -2,22 +2,22 @@
  * @file
  * CSS for Offcanvas tray.
  */
-/* Position the dialog-offcanvas tray container outside the right of the viewport. */
-.ui-dialog-offcanvas {
+/* Position the dialog-off-canvas tray container outside the right of the viewport. */
+.ui-dialog-off-canvas {
   box-sizing: border-box;
   height: 100%;
   overflow: visible;
 }
 
-/* Wrap the form that's inside the dialog-offcanvas tray. */
-.ui-dialog-offcanvas .ui-dialog-content {
+/* Wrap the form that's inside the dialog-off-canvas tray. */
+.ui-dialog-off-canvas .ui-dialog-content {
   padding: 0 20px;
   /* Prevent horizontal scrollbar. */
   overflow-x: hidden;
   overflow-y: auto;
 }
 
-[dir="rtl"] .ui-dialog-offcanvas .ui-dialog-content {
+[dir="rtl"] .ui-dialog-off-canvas .ui-dialog-content {
   text-align: right;
 }
 
@@ -27,7 +27,7 @@
  */
 @media all and (max-width: 48em) {
   /* 768px */
-  .ui-dialog.ui-dialog-offcanvas {
+  .ui-dialog.ui-dialog-off-canvas {
     width: 100% !important;
   }
 
diff --git a/core/misc/dialog/offcanvas.js b/core/misc/dialog/off-canvas.js
similarity index 75%
rename from core/misc/dialog/offcanvas.js
rename to core/misc/dialog/off-canvas.js
index 7493e0a..3d37fd6 100644
--- a/core/misc/dialog/offcanvas.js
+++ b/core/misc/dialog/off-canvas.js
@@ -8,7 +8,7 @@
   'use strict';
 
   // The minimum width to use body displace needs to match the width at which
-  // the tray will be %100 width. @see offcanvas.css
+  // the tray will be %100 width. @see off-canvas.css
   var minDisplaceWidth = 768;
 
   /**
@@ -18,7 +18,7 @@
    */
   var edge = document.documentElement.dir === 'rtl' ? 'left' : 'right';
 
-  var $mainCanvasWrapper = $('[data-offcanvas-main-canvas]');
+  var $mainCanvasWrapper = $('[data-off-canvas-main-canvas]');
 
   /**
    * Resets the size of the dialog.
@@ -47,7 +47,7 @@
 
     $element
       .dialog('option', adjustedOptions)
-      .trigger('dialogContentResize.offcanvas');
+      .trigger('dialogContentResize.off-canvas');
   }
 
   /**
@@ -60,7 +60,7 @@
     var $element = event.data.$element;
     var $widget = $element.dialog('widget');
 
-    var $offsets = $widget.find('> :not(#drupal-offcanvas, .ui-resizable-handle)');
+    var $offsets = $widget.find('> :not(#drupal-off-canvas, .ui-resizable-handle)');
     var offset = 0;
     var modalHeight;
 
@@ -98,25 +98,25 @@
 
   $(window).on({
     'dialog:aftercreate': function (event, dialog, $element, settings) {
-      if ($element.is('#drupal-offcanvas')) {
+      if ($element.is('#drupal-off-canvas')) {
         var eventData = {settings: settings, $element: $element};
-        $('.ui-dialog-offcanvas, .ui-dialog-offcanvas .ui-dialog-titlebar').toggleClass('ui-dialog-empty-title', !settings.title);
+        $('.ui-dialog-off-canvas, .ui-dialog-off-canvas .ui-dialog-titlebar').toggleClass('ui-dialog-empty-title', !settings.title);
 
         $element
-          .on('dialogresize.offcanvas', eventData, debounce(bodyPadding, 100))
-          .on('dialogContentResize.offcanvas', eventData, handleDialogResize)
-          .on('dialogContentResize.offcanvas', eventData, debounce(bodyPadding, 100))
-          .trigger('dialogresize.offcanvas');
+          .on('dialogresize.off-canvas', eventData, debounce(bodyPadding, 100))
+          .on('dialogContentResize.off-canvas', eventData, handleDialogResize)
+          .on('dialogContentResize.off-canvas', eventData, debounce(bodyPadding, 100))
+          .trigger('dialogresize.off-canvas');
 
         $element.dialog('widget').attr('data-offset-' + edge, '');
 
         $(window)
-          .on('resize.offcanvas scroll.offcanvas', eventData, debounce(resetSize, 100))
-          .trigger('resize.offcanvas');
+          .on('resize.off-canvas scroll.off-canvas', eventData, debounce(resetSize, 100))
+          .trigger('resize.off-canvas');
       }
     },
     'dialog:beforecreate': function (event, dialog, $element, settings) {
-      if ($element.is('#drupal-offcanvas')) {
+      if ($element.is('#drupal-off-canvas')) {
         $('body').addClass('js-tray-open');
         // @see http://api.jqueryui.com/position/
         settings.position = {
@@ -124,17 +124,17 @@
           at: edge + ' top',
           of: window
         };
-        settings.dialogClass += ' ui-dialog-offcanvas';
+        settings.dialogClass += ' ui-dialog-off-canvas';
         // Applies initial height to dialog based on window height.
         // See http://api.jqueryui.com/dialog for all dialog options.
         settings.height = $(window).height();
       }
     },
     'dialog:beforeclose': function (event, dialog, $element) {
-      if ($element.is('#drupal-offcanvas')) {
+      if ($element.is('#drupal-off-canvas')) {
         $('body').removeClass('js-tray-open');
-        $(document).off('.offcanvas');
-        $(window).off('.offcanvas');
+        $(document).off('.off-canvas');
+        $(window).off('.off-canvas');
         $mainCanvasWrapper.css('padding-' + edge, 0);
       }
     }
diff --git a/core/misc/dialog/offcanvas.motion.css b/core/misc/dialog/off-canvas.motion.css
similarity index 86%
rename from core/misc/dialog/offcanvas.motion.css
rename to core/misc/dialog/off-canvas.motion.css
index 7228a29..c1379be 100644
--- a/core/misc/dialog/offcanvas.motion.css
+++ b/core/misc/dialog/off-canvas.motion.css
@@ -10,21 +10,21 @@
  */
 
 /* Transition the dialog-offcanvas tray container, with 2s delay to match main canvas speed. */
-.ui-dialog-offcanvas .ui-dialog-content {
+.ui-dialog-off-canvas .ui-dialog-content {
   -webkit-transition: all .7s ease 2s;
   -moz-transition: all .7s ease 2s;
   transition: all .7s ease 2s;
 }
 
 @media (max-width: 700px) {
-  .ui-dialog-offcanvas .ui-dialog-content {
+  .ui-dialog-off-canvas .ui-dialog-content {
     -webkit-transition: all .7s ease;
     -moz-transition: all .7s ease;
     transition: all .7s ease;
   }
 }
 
-.dialog-offcanvas__main-canvas {
+.dialog-off-canvas__main-canvas {
   -webkit-transition: all .7s ease;
   -moz-transition: all .7s ease;
   transition: all .7s ease;
diff --git a/core/modules/outside_in/css/outside_in.motion.css b/core/modules/outside_in/css/outside_in.motion.css
index 1177225..61d68b7 100644
--- a/core/modules/outside_in/css/outside_in.motion.css
+++ b/core/modules/outside_in/css/outside_in.motion.css
@@ -15,9 +15,9 @@
 }
 
 /* Transition the editables on the page, their contextual links and their hover states. */
-.dialog-offcanvas__main-canvas .contextual,
-.dialog-offcanvas__main-canvas .js-outside-in-edit-mode .outside-in-editable,
-.dialog-offcanvas__main-canvas.js-tray-open .js-outside-in-edit-mode .outside-in-editable {
+.dialog-off-canvas__main-canvas .contextual,
+.dialog-off-canvas__main-canvas .js-outside-in-edit-mode .outside-in-editable,
+.dialog-off-canvas__main-canvas.js-tray-open .js-outside-in-edit-mode .outside-in-editable {
   -webkit-transition: all .7s ease;
   -moz-transition: all .7s ease;
   transition: all .7s ease;
diff --git a/core/modules/outside_in/css/outside_in.theme.css b/core/modules/outside_in/css/outside_in.theme.css
index 91c01ab..011d198 100644
--- a/core/modules/outside_in/css/outside_in.theme.css
+++ b/core/modules/outside_in/css/outside_in.theme.css
@@ -60,16 +60,16 @@
 }
 
 /* Style the editables while in edit mode. */
-.dialog-offcanvas__main-canvas.js-outside-in-edit-mode .outside-in-editable {
+.dialog-off-canvas__main-canvas.js-outside-in-edit-mode .outside-in-editable {
   outline: 1px dashed rgba(0,0,0,0.5);
   box-shadow: 0 0 0 1px rgba(255,255,255,0.7);
 }
-.dialog-offcanvas__main-canvas.js-outside-in-edit-mode .outside-in-editable:hover,
-.dialog-offcanvas__main-canvas.js-outside-in-edit-mode .outside-in-editable.outside-in-active-editable {
+.dialog-off-canvas__main-canvas.js-outside-in-edit-mode .outside-in-editable:hover,
+.dialog-off-canvas__main-canvas.js-outside-in-edit-mode .outside-in-editable.outside-in-active-editable {
   background-color: rgba(0,0,0,0.2);
 }
 
-/* Style the dialog-offcanvas container. */
+/* Style the dialog-off-canvas container. */
 .ui-dialog-outside-in {
   background: #444;
   border: 0 solid transparent;
diff --git a/core/modules/outside_in/js/outside_in.js b/core/modules/outside_in/js/outside_in.js
index 650af46..9ec88de 100644
--- a/core/modules/outside_in/js/outside_in.js
+++ b/core/modules/outside_in/js/outside_in.js
@@ -9,7 +9,7 @@
 
   var blockConfigureSelector = '[data-outside-in-edit]';
   var toggleEditSelector = '[data-drupal-outsidein="toggle"]';
-  var itemsToToggleSelector = '[data-offcanvas-main-canvas], #toolbar-bar, [data-drupal-outsidein="editable"] a, [data-drupal-outsidein="editable"] button';
+  var itemsToToggleSelector = '[data-off-canvas-main-canvas], #toolbar-bar, [data-drupal-outsidein="editable"] a, [data-drupal-outsidein="editable"] button';
   var contextualItemsSelector = '[data-contextual-id] a, [data-contextual-id] button';
   var quickEditItemSelector = '[data-quickedit-entity-id]';
 
@@ -115,10 +115,10 @@
   }
 
   /**
-   * Closes/removes offcanvas.
+   * Closes/removes off canvas.
    */
   function closeOffCanvas() {
-    $('.ui-dialog-offcanvas .ui-dialog-titlebar-close').trigger('click');
+    $('.ui-dialog-off-canvas .ui-dialog-titlebar-close').trigger('click');
   }
 
   /**
@@ -139,7 +139,7 @@
       $editables = $('[data-drupal-outsidein="editable"]').once('outsidein');
       if ($editables.length) {
         // Use event capture to prevent clicks on links.
-        document.querySelector('[data-offcanvas-main-canvas]').addEventListener('click', preventClick, true);
+        document.querySelector('[data-off-canvas-main-canvas]').addEventListener('click', preventClick, true);
 
         // When a click occurs try and find the outside-in edit link
         // and click it.
@@ -172,7 +172,7 @@
     else {
       $editables = $('[data-drupal-outsidein="editable"]').removeOnce('outsidein');
       if ($editables.length) {
-        document.querySelector('[data-offcanvas-main-canvas]').removeEventListener('click', preventClick, true);
+        document.querySelector('[data-off-canvas-main-canvas]').removeEventListener('click', preventClick, true);
         $editables.off('.outsidein');
         $(quickEditItemSelector).off('.outsidein');
       }
@@ -220,7 +220,7 @@
           var hasElement = instance && !!instance.element;
           var rendererOffcanvas = false;
           if (hasElement) {
-            rendererOffcanvas = $(instance.element).attr('data-dialog-renderer') === 'offcanvas';
+            rendererOffcanvas = $(instance.element).attr('data-dialog-renderer') === 'off_canvas';
           }
           return hasElement && rendererOffcanvas;
         })
@@ -238,7 +238,7 @@
   // Manage Active editable class on opening and closing of the dialog.
   $(window).on({
     'dialog:beforecreate': function (event, dialog, $element, settings) {
-      if ($element.is('#drupal-offcanvas')) {
+      if ($element.is('#drupal-off-canvas')) {
         $('body .outside-in-active-editable').removeClass('outside-in-active-editable');
         var $activeElement = $('#' + settings.outsideInActiveEditableId);
         if ($activeElement.length) {
@@ -248,7 +248,7 @@
       }
     },
     'dialog:beforeclose': function (event, dialog, $element) {
-      if ($element.is('#drupal-offcanvas')) {
+      if ($element.is('#drupal-off-canvas')) {
         $('body .outside-in-active-editable').removeClass('outside-in-active-editable');
       }
     }
diff --git a/core/modules/outside_in/outside_in.links.contextual.yml b/core/modules/outside_in/outside_in.links.contextual.yml
index 99b36ef..b0c0f13 100644
--- a/core/modules/outside_in/outside_in.links.contextual.yml
+++ b/core/modules/outside_in/outside_in.links.contextual.yml
@@ -1,4 +1,4 @@
 outside_in.block_configure:
   title: 'Quick edit'
-  route_name: 'entity.block.offcanvas_form'
+  route_name: 'entity.block.off_canvas_form'
   group: 'block'
diff --git a/core/modules/outside_in/outside_in.module b/core/modules/outside_in/outside_in.module
index 54a3525..3da4520 100644
--- a/core/modules/outside_in/outside_in.module
+++ b/core/modules/outside_in/outside_in.module
@@ -30,14 +30,14 @@ function outside_in_help($route_name, RouteMatchInterface $route_match) {
 /**
  * Implements hook_contextual_links_view_alter().
  *
- * Change Configure Blocks into offcanvas links.
+ * Change Configure Blocks into off canvas links.
  */
 function outside_in_contextual_links_view_alter(&$element, $items) {
   if (isset($element['#links']['outside-inblock-configure'])) {
     $element['#links']['outside-inblock-configure']['attributes'] = [
       'class' => ['use-ajax'],
       'data-dialog-type' => 'dialog',
-      'data-dialog-renderer' => 'offcanvas',
+      'data-dialog-renderer' => 'off_canvas',
       'data-outside-in-edit' => TRUE,
     ];
 
@@ -63,8 +63,8 @@ function outside_in_block_view_alter(array &$build) {
 function outside_in_entity_type_build(array &$entity_types) {
   /* @var $entity_types \Drupal\Core\Entity\EntityTypeInterface[] */
   $entity_types['block']
-    ->setFormClass('offcanvas', BlockEntityOffCanvasForm::class)
-    ->setLinkTemplate('offcanvas-form', '/admin/structure/block/manage/{block}/offcanvas');
+    ->setFormClass('off_canvas', BlockEntityOffCanvasForm::class)
+    ->setLinkTemplate('off_canvas-form', '/admin/structure/block/manage/{block}/off-canvas');
 }
 
 /**
@@ -110,14 +110,14 @@ function outside_in_toolbar_alter(&$items) {
  */
 function outside_in_block_alter(&$definitions) {
   if (!empty($definitions['system_branding_block'])) {
-    $definitions['system_branding_block']['forms']['offcanvas'] = SystemBrandingOffCanvasForm::class;
+    $definitions['system_branding_block']['forms']['off_canvas'] = SystemBrandingOffCanvasForm::class;
   }
 
   // Since menu blocks use derivatives, check the definition ID instead of
   // relying on the plugin ID.
   foreach ($definitions as &$definition) {
     if ($definition['id'] === 'system_menu_block') {
-      $definition['forms']['offcanvas'] = SystemMenuOffCanvasForm::class;
+      $definition['forms']['off_canvas'] = SystemMenuOffCanvasForm::class;
     }
   }
 }
diff --git a/core/modules/outside_in/outside_in.routing.yml b/core/modules/outside_in/outside_in.routing.yml
index 79bc38d..18a564c 100644
--- a/core/modules/outside_in/outside_in.routing.yml
+++ b/core/modules/outside_in/outside_in.routing.yml
@@ -1,7 +1,7 @@
-entity.block.offcanvas_form:
-  path: '/admin/structure/block/manage/{block}/offcanvas'
+entity.block.off_canvas_form:
+  path: '/admin/structure/block/manage/{block}/off-canvas'
   defaults:
-    _entity_form: 'block.offcanvas'
+    _entity_form: 'block.off_canvas'
     _title_callback: '\Drupal\outside_in\Block\BlockEntityOffCanvasForm::title'
   requirements:
     _permission: 'administer blocks'
diff --git a/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
index a77f51f..1d6ea37 100644
--- a/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
+++ b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
@@ -92,7 +92,7 @@ protected function submitVisibility(array $form, FormStateInterface $form_state)
    */
   protected function getPluginForm(BlockPluginInterface $block) {
     if ($block instanceof PluginWithFormsInterface) {
-      return $this->pluginFormFactory->createInstance($block, 'offcanvas', 'configure');
+      return $this->pluginFormFactory->createInstance($block, 'off_canvas', 'configure');
     }
     return $block;
   }
diff --git a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
index c39f2f8..4242620 100644
--- a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
+++ b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
@@ -119,14 +119,14 @@ public function testBlocks($block_id, $new_page_text, $element_selector, $label_
 
     // Exit edit mode using ESC.
     $web_assert->elementTextContains('css', '.contextual-toolbar-tab button', 'Editing');
-    $web_assert->elementAttributeContains('css', '.dialog-offcanvas__main-canvas', 'class', 'js-outside-in-edit-mode');
+    $web_assert->elementAttributeContains('css', '.dialog-off-canvas__main-canvas', 'class', 'js-outside-in-edit-mode');
     // Simulate press the Escape key.
     $this->getSession()->executeScript('jQuery("body").trigger(jQuery.Event("keyup", { keyCode: 27 }));');
     $this->waitForOffCanvasToClose();
     $this->getSession()->wait(100);
     $web_assert->elementTextContains('css', '#drupal-live-announce', 'Exited edit mode.');
     $web_assert->elementTextNotContains('css', '.contextual-toolbar-tab button', 'Editing');
-    $web_assert->elementAttributeNotContains('css', '.dialog-offcanvas__main-canvas', 'class', 'js-outside-in-edit-mode');
+    $web_assert->elementAttributeNotContains('css', '.dialog-off-canvas__main-canvas', 'class', 'js-outside-in-edit-mode');
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php b/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php
index 0debdc8..ca0ce04 100644
--- a/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php
+++ b/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php
@@ -13,7 +13,7 @@
 class OffCanvasDialogTest extends AjaxTestBase {
 
   /**
-   * Test sending AJAX requests to open and manipulate offcanvas dialog.
+   * Test sending AJAX requests to open and manipulate off canvas dialog.
    */
   public function testDialog() {
     $this->drupalLogin($this->drupalCreateUser(['administer contact forms']));
@@ -24,9 +24,9 @@ public function testDialog() {
     $dialog_renderable = AjaxTestController::dialogContents();
     $dialog_contents = \Drupal::service('renderer')->renderRoot($dialog_renderable);
 
-    $offcanvas_expected_response = [
+    $off_canvas_expected_response = [
       'command' => 'openDialog',
-      'selector' => '#drupal-offcanvas',
+      'selector' => '#drupal-off-canvas',
       'settings' => NULL,
       'data' => $dialog_contents,
       'dialogOptions' =>
@@ -44,8 +44,8 @@ public function testDialog() {
     ];
 
     // Emulate going to the JS version of the page and check the JSON response.
-    $ajax_result = $this->drupalGetAjax('ajax-test/dialog-contents', ['query' => [MainContentViewSubscriber::WRAPPER_FORMAT => 'drupal_dialog.offcanvas']]);
-    $this->assertEqual($offcanvas_expected_response, $ajax_result[3], 'Off-canvas dialog JSON response matches.');
+    $ajax_result = $this->drupalGetAjax('ajax-test/dialog-contents', ['query' => [MainContentViewSubscriber::WRAPPER_FORMAT => 'drupal_dialog.off_canvas']]);
+    $this->assertEqual($off_canvas_expected_response, $ajax_result[3], 'Off-canvas dialog JSON response matches.');
   }
 
 }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 043fc0f..d5e14ef 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -224,7 +224,7 @@ function system_theme() {
       ),
       'template' => 'entity-add-list',
     ),
-    'offcanvas_page_wrapper' => [
+    'off_canvas_page_wrapper' => [
       'variables' => ['children' => NULL],
     ],
   ));
@@ -1454,6 +1454,6 @@ function system_query_entity_reference_alter(AlterableInterface $query) {
  */
 function system_element_info_alter(&$type) {
   if (isset($type['page'])) {
-    $type['page']['#theme_wrappers']['offcanvas_page_wrapper'] = ['#weight' => -1000];
+    $type['page']['#theme_wrappers']['off_canvas_page_wrapper'] = ['#weight' => -1000];
   }
 }
diff --git a/core/themes/stable/templates/layout/offcanvas-page-wrapper.html.twig b/core/modules/system/templates/off-canvas-page-wrapper.html.twig
similarity index 80%
rename from core/themes/stable/templates/layout/offcanvas-page-wrapper.html.twig
rename to core/modules/system/templates/off-canvas-page-wrapper.html.twig
index adedc6b..c2f5fb9 100644
--- a/core/themes/stable/templates/layout/offcanvas-page-wrapper.html.twig
+++ b/core/modules/system/templates/off-canvas-page-wrapper.html.twig
@@ -12,7 +12,7 @@
  */
 #}
 {% if children %}
-  <div class="dialog-offcanvas__main-canvas" data-offcanvas-main-canvas >
+  <div class="dialog-off-canvas__main-canvas" data-off-canvas-main-canvas >
     {{ children }}
   </div>
 {% endif %}
diff --git a/core/modules/system/tests/modules/offcanvas_test/offcanvas_test.info.yml b/core/modules/system/tests/modules/off_canvas_test/off_canvas_test.info.yml
similarity index 100%
rename from core/modules/system/tests/modules/offcanvas_test/offcanvas_test.info.yml
rename to core/modules/system/tests/modules/off_canvas_test/off_canvas_test.info.yml
diff --git a/core/modules/system/tests/modules/off_canvas_test/off_canvas_test.routing.yml b/core/modules/system/tests/modules/off_canvas_test/off_canvas_test.routing.yml
new file mode 100644
index 0000000..4ae56c4
--- /dev/null
+++ b/core/modules/system/tests/modules/off_canvas_test/off_canvas_test.routing.yml
@@ -0,0 +1,29 @@
+off_canvas_test.links:
+  path: '/off-canvas-test-links'
+  defaults:
+    _controller: '\Drupal\off_canvas_test\Controller\TestController::linksDisplay'
+    _title: 'Links'
+  requirements:
+    _access: 'TRUE'
+
+off_canvas_test.thing1:
+  path: '/off-canvas-thing1'
+  defaults:
+    _controller: '\Drupal\off_canvas_test\Controller\TestController::thing1'
+    _title: 'Thing 1'
+  requirements:
+    _access: 'TRUE'
+
+off_canvas_test.thing2:
+  path: '/off-canvas-thing2'
+  defaults:
+    _controller: '\Drupal\off_canvas_test\Controller\TestController::thing2'
+  requirements:
+    _access: 'TRUE'
+
+off_canvas_test.dialog_links:
+  path: '/off-canvas-dialog-links'
+  defaults:
+    _controller: '\Drupal\off_canvas_test\Controller\TestController::otherDialogLinks'
+  requirements:
+    _access: 'TRUE'
diff --git a/core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php b/core/modules/system/tests/modules/off_canvas_test/src/Controller/TestController.php
similarity index 73%
rename from core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php
rename to core/modules/system/tests/modules/off_canvas_test/src/Controller/TestController.php
index e5fae3d..b69a340 100644
--- a/core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php
+++ b/core/modules/system/tests/modules/off_canvas_test/src/Controller/TestController.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\offcanvas_test\Controller;
+namespace Drupal\off_canvas_test\Controller;
 
 use Drupal\Component\Serialization\Json;
 use Drupal\Core\Url;
@@ -37,21 +37,21 @@ public function thing2() {
   }
 
   /**
-   * Displays test links that will open in offcanvas tray.
+   * Displays test links that will open in off canvas tray.
    *
    * @return array
    *   Render array with links.
    */
   public function linksDisplay() {
     return [
-      'offcanvas_link_1' => [
+      'off_canvas_link_1' => [
         '#title' => 'Click Me 1!',
         '#type' => 'link',
-        '#url' => Url::fromRoute('offcanvas_test.thing1'),
+        '#url' => Url::fromRoute('off_canvas_test.thing1'),
         '#attributes' => [
           'class' => ['use-ajax'],
           'data-dialog-type' => 'dialog',
-          'data-dialog-renderer' => 'offcanvas',
+          'data-dialog-renderer' => 'off_canvas',
         ],
         '#attached' => [
           'library' => [
@@ -59,14 +59,14 @@ public function linksDisplay() {
           ],
         ],
       ],
-      'offcanvas_link_2' => [
+      'off_canvas_link_2' => [
         '#title' => 'Click Me 2!',
         '#type' => 'link',
-        '#url' => Url::fromRoute('offcanvas_test.thing2'),
+        '#url' => Url::fromRoute('off_canvas_test.thing2'),
         '#attributes' => [
           'class' => ['use-ajax'],
           'data-dialog-type' => 'dialog',
-          'data-dialog-renderer' => 'offcanvas',
+          'data-dialog-renderer' => 'off_canvas',
           'data-dialog-options' => Json::encode([
             'width' => 555,
           ]),
@@ -80,11 +80,11 @@ public function linksDisplay() {
       'other_dialog_links' => [
         '#title' => 'Display more links!',
         '#type' => 'link',
-        '#url' => Url::fromRoute('offcanvas_test.dialog_links'),
+        '#url' => Url::fromRoute('off_canvas_test.dialog_links'),
         '#attributes' => [
           'class' => ['use-ajax'],
           'data-dialog-type' => 'dialog',
-          'data-dialog-renderer' => 'offcanvas',
+          'data-dialog-renderer' => 'off_canvas',
         ],
         '#attached' => [
           'library' => [
@@ -96,12 +96,12 @@ public function linksDisplay() {
   }
 
   /**
-   * Displays dialogs links to be displayed inside the offcanvas tray.
+   * Displays dialogs links to be displayed inside the off canvas tray.
    *
-   * This links are used to test opening a modal and another offcanvas link from
-   * inside the offcanvas tray.
+   * This links are used to test opening a modal and another off canvas link from
+   * inside the off canvas tray.
    *
-   * @todo Update tests to check these links work in the offcanvas tray.
+   * @todo Update tests to check these links work in the off canvas tray.
    *       https://www.drupal.org/node/2790073
    *
    * @return array
@@ -113,19 +113,19 @@ public function otherDialogLinks() {
       '#links' => [
         'modal_link' => [
           'title' => 'Open modal!',
-          'url' => Url::fromRoute('offcanvas_test.thing2'),
+          'url' => Url::fromRoute('off_canvas_test.thing2'),
           'attributes' => [
             'class' => ['use-ajax'],
             'data-dialog-type' => 'modal',
           ],
         ],
-        'offcanvas_link' => [
+        'off_canvas_link' => [
           'title' => 'Offcanvas link!',
-          'url' => Url::fromRoute('offcanvas_test.thing2'),
+          'url' => Url::fromRoute('off_canvas_test.thing2'),
           'attributes' => [
             'class' => ['use-ajax'],
             'data-dialog-type' => 'dialog',
-            'data-dialog-renderer' => 'offcanvas',
+            'data-dialog-renderer' => 'off_canvas',
           ],
         ],
       ],
diff --git a/core/modules/system/tests/modules/offcanvas_test/offcanvas_test.routing.yml b/core/modules/system/tests/modules/offcanvas_test/offcanvas_test.routing.yml
deleted file mode 100644
index 761693b..0000000
--- a/core/modules/system/tests/modules/offcanvas_test/offcanvas_test.routing.yml
+++ /dev/null
@@ -1,29 +0,0 @@
-offcanvas_test.links:
-  path: '/offcanvas-test-links'
-  defaults:
-    _controller: '\Drupal\offcanvas_test\Controller\TestController::linksDisplay'
-    _title: 'Links'
-  requirements:
-    _access: 'TRUE'
-
-offcanvas_test.thing1:
-  path: '/offcanvas-thing1'
-  defaults:
-    _controller: '\Drupal\offcanvas_test\Controller\TestController::thing1'
-    _title: 'Thing 1'
-  requirements:
-    _access: 'TRUE'
-
-offcanvas_test.thing2:
-  path: '/offcanvas-thing2'
-  defaults:
-    _controller: '\Drupal\offcanvas_test\Controller\TestController::thing2'
-  requirements:
-    _access: 'TRUE'
-
-offcanvas_test.dialog_links:
-  path: '/offcanvas-dialog-links'
-  defaults:
-    _controller: '\Drupal\offcanvas_test\Controller\TestController::otherDialogLinks'
-  requirements:
-    _access: 'TRUE'
diff --git a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
index dc4b332..bfcda1c 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
@@ -12,7 +12,7 @@ class OffCanvasTest extends OffCanvasTestBase {
   /**
    * {@inheritdoc}
    */
-  public static $modules = ['block', 'system', 'toolbar', 'offcanvas_test'];
+  public static $modules = ['block', 'system', 'toolbar', 'off_canvas_test'];
 
   /**
    * Tests that regular non-contextual links will work with the off-canvas tray.
@@ -22,13 +22,13 @@ public function testOffCanvasLinks() {
     // Test the same functionality on multiple themes.
     foreach ($themes as $theme) {
       $this->enableTheme($theme);
-      $this->drupalGet('/offcanvas-test-links');
+      $this->drupalGet('/off-canvas-test-links');
 
       $page = $this->getSession()->getPage();
       $web_assert = $this->assertSession();
 
       // Make sure off-canvas tray is on page when first loaded.
-      $web_assert->elementNotExists('css', '#drupal-offcanvas');
+      $web_assert->elementNotExists('css', '#drupal-off-canvas');
 
       // Check opening and closing with two separate links.
       // Make sure tray updates to new content.
@@ -40,16 +40,16 @@ public function testOffCanvasLinks() {
         $this->waitForOffCanvasToOpen();
 
         // Check that the canvas is not on the page.
-        $web_assert->elementExists('css', '#drupal-offcanvas');
+        $web_assert->elementExists('css', '#drupal-off-canvas');
         // Check that response text is on page.
         $web_assert->pageTextContains("Thing $link_index says hello");
-        $offcanvas_tray = $this->getTray();
+        $off_canvas_tray = $this->getTray();
 
         // Check that tray is visible.
-        $this->assertEquals(TRUE, $offcanvas_tray->isVisible());
-        $header_text = $offcanvas_tray->find('css', '.ui-dialog-title')->getText();
+        $this->assertEquals(TRUE, $off_canvas_tray->isVisible());
+        $header_text = $off_canvas_tray->find('css', '.ui-dialog-title')->getText();
 
-        $tray_text = $offcanvas_tray->findById('drupal-offcanvas')->getText();
+        $tray_text = $off_canvas_tray->findById('drupal-off-canvas')->getText();
         $this->assertEquals("Thing $link_index says hello", $tray_text);
 
         if ($link_index == '2') {
@@ -57,7 +57,7 @@ public function testOffCanvasLinks() {
           $web_assert->elementExists('css', '.ui-dialog-empty-title');
           $this->assertEquals('', $header_text);
 
-          $style = $page->find('css', '.ui-dialog-offcanvas')->getAttribute('style');
+          $style = $page->find('css', '.ui-dialog-off-canvas')->getAttribute('style');
           self::assertTrue(strstr($style, 'width: 555px;') !== FALSE, 'Dialog width respected.');
         }
         else {
@@ -85,21 +85,21 @@ public function testNarrowWidth() {
       $this->enableTheme($theme);
       // Testing at the wider width.
       $this->getSession()->resizeWindow($narrow_width_breakpoint + $offset, $height);
-      $this->drupalGet('/offcanvas-test-links');
-      $this->assertFalse($page->find('css', '.dialog-offcanvas__main-canvas')->hasAttribute('style'), 'Body not padded on wide page load.');
+      $this->drupalGet('/off-canvas-test-links');
+      $this->assertFalse($page->find('css', '.dialog-off-canvas__main-canvas')->hasAttribute('style'), 'Body not padded on wide page load.');
       $page->clickLink("Click Me 1!");
       $this->waitForOffCanvasToOpen();
       // Check that the main canvas is padded when page is not narrow width and
       // tray is open.
-      $web_assert->elementAttributeContains('css', '.dialog-offcanvas__main-canvas', 'style', 'padding-right');
+      $web_assert->elementAttributeContains('css', '.dialog-off-canvas__main-canvas', 'style', 'padding-right');
 
       // Testing at the narrower width.
       $this->getSession()->resizeWindow($narrow_width_breakpoint - $offset, $height);
-      $this->drupalGet('/offcanvas-test-links');
-      $this->assertFalse($page->find('css', '.dialog-offcanvas__main-canvas')->hasAttribute('style'), 'Body not padded on narrow page load.');
+      $this->drupalGet('/off-canvas-test-links');
+      $this->assertFalse($page->find('css', '.dialog-off-canvas__main-canvas')->hasAttribute('style'), 'Body not padded on narrow page load.');
       $page->clickLink("Click Me 1!");
       $this->waitForOffCanvasToOpen();
-      $this->assertFalse($page->find('css', '.dialog-offcanvas__main-canvas')->hasAttribute('style'), 'Body not padded on narrow page with tray open.');
+      $this->assertFalse($page->find('css', '.dialog-off-canvas__main-canvas')->hasAttribute('style'), 'Body not padded on narrow page with tray open.');
     }
   }
 
diff --git a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTestBase.php b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTestBase.php
index 9358b08..bcd56a7 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTestBase.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTestBase.php
@@ -15,7 +15,7 @@
   protected function waitForOffCanvasToOpen() {
     $web_assert = $this->assertSession();
     $web_assert->assertWaitOnAjaxRequest();
-    $this->waitForElement('#drupal-offcanvas');
+    $this->waitForElement('#drupal-off-canvas');
   }
 
   /**
@@ -62,7 +62,7 @@ public function enableTheme($theme) {
    * Waits for Off-canvas tray to close.
    */
   protected function waitForOffCanvasToClose() {
-    $this->waitForNoElement('#drupal-offcanvas');
+    $this->waitForNoElement('#drupal-off-canvas');
   }
 
   /**
@@ -85,7 +85,7 @@ protected function waitForNoElement($selector, $timeout = 10000) {
    *   The tray page element.
    */
   protected function getTray() {
-    $tray = $this->getSession()->getPage()->find('css', '.ui-dialog[aria-describedby="drupal-offcanvas"]');
+    $tray = $this->getSession()->getPage()->find('css', '.ui-dialog[aria-describedby="drupal-off-canvas"]');
     $this->assertEquals(FALSE, empty($tray), 'The tray was found.');
     return $tray;
   }
diff --git a/core/modules/system/tests/src/Unit/Ajax/OpenOffCanvasDialogCommandTest.php b/core/modules/system/tests/src/Unit/Ajax/OpenOffCanvasDialogCommandTest.php
index 5ef060f..1bed8a1 100644
--- a/core/modules/system/tests/src/Unit/Ajax/OpenOffCanvasDialogCommandTest.php
+++ b/core/modules/system/tests/src/Unit/Ajax/OpenOffCanvasDialogCommandTest.php
@@ -19,7 +19,7 @@ public function testRender() {
 
     $expected = [
       'command' => 'openDialog',
-      'selector' => '#drupal-offcanvas',
+      'selector' => '#drupal-off-canvas',
       'settings' => NULL,
       'data' => '<p>Text!</p>',
       'dialogOptions' => [
diff --git a/core/themes/stable/css/core/dialog/offcanvas.css b/core/themes/stable/css/core/dialog/off-canvas.css
similarity index 81%
rename from core/themes/stable/css/core/dialog/offcanvas.css
rename to core/themes/stable/css/core/dialog/off-canvas.css
index 0e46c6a..cf5f47f 100644
--- a/core/themes/stable/css/core/dialog/offcanvas.css
+++ b/core/themes/stable/css/core/dialog/off-canvas.css
@@ -3,21 +3,21 @@
  * CSS for Offcanvas tray.
  */
 /* Position the dialog-offcanvas tray container outside the right of the viewport. */
-.ui-dialog-offcanvas {
+.ui-dialog-off-canvas {
   box-sizing: border-box;
   height: 100%;
   overflow: visible;
 }
 
 /* Wrap the form that's inside the dialog-offcanvas tray. */
-.ui-dialog-offcanvas .ui-dialog-content {
+.ui-dialog-off-canvas .ui-dialog-content {
   padding: 0 20px;
   /* Prevent horizontal scrollbar. */
   overflow-x: hidden;
   overflow-y: auto;
 }
 
-[dir="rtl"] .ui-dialog-offcanvas .ui-dialog-content {
+[dir="rtl"] .ui-dialog-off-canvas .ui-dialog-content {
   text-align: right;
 }
 
@@ -27,7 +27,7 @@
  */
 @media all and (max-width: 48em) {
   /* 768px */
-  .ui-dialog.ui-dialog-offcanvas {
+  .ui-dialog.ui-dialog-off-canvas {
     width: 100% !important;
   }
 
diff --git a/core/themes/stable/css/core/dialog/offcanvas.motion.css b/core/themes/stable/css/core/dialog/off-canvas.motion.css
similarity index 86%
rename from core/themes/stable/css/core/dialog/offcanvas.motion.css
rename to core/themes/stable/css/core/dialog/off-canvas.motion.css
index 7228a29..c1379be 100644
--- a/core/themes/stable/css/core/dialog/offcanvas.motion.css
+++ b/core/themes/stable/css/core/dialog/off-canvas.motion.css
@@ -10,21 +10,21 @@
  */
 
 /* Transition the dialog-offcanvas tray container, with 2s delay to match main canvas speed. */
-.ui-dialog-offcanvas .ui-dialog-content {
+.ui-dialog-off-canvas .ui-dialog-content {
   -webkit-transition: all .7s ease 2s;
   -moz-transition: all .7s ease 2s;
   transition: all .7s ease 2s;
 }
 
 @media (max-width: 700px) {
-  .ui-dialog-offcanvas .ui-dialog-content {
+  .ui-dialog-off-canvas .ui-dialog-content {
     -webkit-transition: all .7s ease;
     -moz-transition: all .7s ease;
     transition: all .7s ease;
   }
 }
 
-.dialog-offcanvas__main-canvas {
+.dialog-off-canvas__main-canvas {
   -webkit-transition: all .7s ease;
   -moz-transition: all .7s ease;
   transition: all .7s ease;
diff --git a/core/themes/stable/stable.info.yml b/core/themes/stable/stable.info.yml
index 7efa1e0..3aceac6 100644
--- a/core/themes/stable/stable.info.yml
+++ b/core/themes/stable/stable.info.yml
@@ -68,8 +68,8 @@ libraries-override:
   core/drupal.dialog.off_canvas:
       css:
         component:
-          misc/dialog/offcanvas.css: css/core/dialog/offcanvas.css
-          misc/dialog/offcanvas.motion.css: css/core/dialog/offcanvas.motion.css
+          misc/dialog/off-canvas.css: css/core/dialog/off-canvas.css
+          misc/dialog/off-canvas.motion.css: css/core/dialog/off-canvas.motion.css
 
   dblog/drupal.dblog:
     css:
diff --git a/core/modules/system/templates/offcanvas-page-wrapper.html.twig b/core/themes/stable/templates/layout/off-canvas-page-wrapper.html.twig
similarity index 80%
rename from core/modules/system/templates/offcanvas-page-wrapper.html.twig
rename to core/themes/stable/templates/layout/off-canvas-page-wrapper.html.twig
index adedc6b..c2f5fb9 100644
--- a/core/modules/system/templates/offcanvas-page-wrapper.html.twig
+++ b/core/themes/stable/templates/layout/off-canvas-page-wrapper.html.twig
@@ -12,7 +12,7 @@
  */
 #}
 {% if children %}
-  <div class="dialog-offcanvas__main-canvas" data-offcanvas-main-canvas >
+  <div class="dialog-off-canvas__main-canvas" data-off-canvas-main-canvas >
     {{ children }}
   </div>
 {% endif %}