The following code will help you to create the popup in Drupal 8. use \ Drupal \ Core \ Ajax ; function testingPopup () { $response = new AjaxResponse (); $title = $this -> t ( 'Title for the Popup.' ); $form [ '#attached' ][ 'library' ][] = 'core/drupal.dialog.ajax' ; $response -> setAttachments ( $form [ '#attached' ]); $content = '<div class="test-popup-content">' . 'Content in HTML format' . '</div>' ; $options = array ( 'dialogClass' => 'popup-dialog-class' , 'width' => '75%' , ); $modal = new OpenModalDialogCommand ( $title , $content , $options ); $response -> addCommand ( $modal ); return $response ; } You can call the function testingPopup() , you will get the popup.