diff --git a/src/wp-admin/js/customize-nav-menus.js b/src/wp-admin/js/customize-nav-menus.js
index 3e223825c4..0818079656 100644
--- a/src/wp-admin/js/customize-nav-menus.js
+++ b/src/wp-admin/js/customize-nav-menus.js
@@ -537,33 +537,37 @@
 			var menuItem,
 				itemName = $( '#custom-menu-item-name' ),
 				itemUrl = $( '#custom-menu-item-url' ),
-				urlRegex,
-				urlValue;
+				urlRegex;
 
 			if ( ! this.currentMenuControl ) {
 				return;
 			}
 
 			/*
-			 * Copyright (c) 2010-2013 Diego Perini, MIT licensed
-			 * https://gist.github.com/dperini/729294
-			 * see also https://mathiasbynens.be/demo/url-regex
-			 * modified to allow protocol-relative URLs
+			 * Allow URLs including:
+			 * - http://example.com/
+			 * - //example.com
+			 * - /directory/
+			 * - ?query-param
+			 * - #target
+			 * - mailto:foo@example.com
+			 *
+			 * Any further validation will be handled on the server when the setting is attempted to be saved,
+			 * so this pattern does not need to be complete.
 			 */
-			urlRegex = /^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})).?)(?::\d{2,5})?(?:[/?#]\S*)?$/i;
+			urlRegex = /^((\w+:)?\/\/\w.*|\w+:(?!\/\/$)|\/|\?|#)/;
 
-			urlValue = itemUrl.val();
 			if ( '' === itemName.val() ) {
 				itemName.addClass( 'invalid' );
 				return;
-			} else if ( '' === urlValue || 'http://' === urlValue || ! ( '/' === urlValue[0] || urlRegex.test( urlValue ) ) ) {
+			} else if ( ! urlRegex.test( itemUrl.val() ) ) {
 				itemUrl.addClass( 'invalid' );
 				return;
 			}
 
 			menuItem = {
 				'title': itemName.val(),
-				'url': urlValue,
+				'url': itemUrl.val(),
 				'type': 'custom',
 				'type_label': api.Menus.data.l10n.custom_label,
 				'object': 'custom'