Srishti Bankar
--- a/core/misc/dialog/dialog.position.js
+++ b/core/misc/dialog/dialog.position.js
          }
          adjustedOptions[option] = adjustedValue;
        }
+        if (
+          option === 'width' &&
+          parseInt(optionValue, 10) > $(window).width()
--- a/core/misc/dialog/dialog.position.js
+++ b/core/misc/dialog/dialog.position.js
          }
          adjustedOptions[option] = adjustedValue;
        }
+        if (
+          option === 'width' &&
+          parseInt(optionValue, 10) >
+            $(window).width() - (displace.offsets.left + displace.offsets.right)
+        ) {
+          adjustedValue = $(window).width() - 40;
--- a/core/misc/dialog/dialog.position.js
+++ b/core/misc/dialog/dialog.position.js
          }
          adjustedOptions[option] = adjustedValue;
        }
+        if (
+          option === 'width' &&
+          parseInt(optionValue, 10) > $(window).width()
+        ) {
+          if (!event.data.settings.modal) {
+            adjustedValue =
+              $(window).width() -
+              40 -
+              (displace.offsets.left + displace.offsets.right);
--- a/core/misc/dialog/dialog.position.js
+++ b/core/misc/dialog/dialog.position.js
+          option === 'width' &&
+          parseInt(optionValue, 10) > $(window).width()
+        ) {
+          if (!event.data.settings.modal) {
+            adjustedValue =
+              $(window).width() -
+              40 -
+              (displace.offsets.left + displace.offsets.right);
+          } else {
+            adjustedValue = $(window).width() - 40;
+          }
+          adjustedOptions[option] = adjustedValue;
+        }
+        if (
+          option === 'width' &&
+          $(window).width() > parseInt(optionValue, 10)
--- a/core/tests/Drupal/FunctionalJavascriptTests/Dialog/DialogPositionTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Dialog/DialogPositionTest.php
+   * Tests dialog resizing on window resize.
+   */
+  public function testModalWidthResizing() {
+    $this->drupalGet('entity_test/structure/entity_test/fields');
+    $page = $this->getSession()->getPage();
+
+    $page->pressButton('List additional actions');
+    $page->findLink('Delete')->click();
+    $this->assertSession()->assertWaitOnAjaxRequest();
+
+    // Resize the window.
+    $this->getSession()->resizeWindow(785, 805);
+    $dialog = $page->find('css', '[role="dialog"]');
+    $dialog_style = $dialog->getAttribute('style');
+    // Assert that the width has been adjusted on window resize.
+    $this->assertStringContainsString('width: 745', $dialog_style);
--- a/core/misc/dialog/dialog.position.js
+++ b/core/misc/dialog/dialog.position.js
          }
          adjustedOptions[option] = adjustedValue;
        }
+        if (
+          option === 'width' &&
+          parseInt(optionValue, 10) > $(window).width()