diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 0a95132681a..7296c02cd3d 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -4,6 +4,7 @@ Yii Framework 2 Change Log
 2.0.50 under development
 ------------------------
 
+- Bug #17181: Improved `BaseUrl::isRelative($url)` performance (sammousa, bizley, rob006)
 - Bug #17191: Fixed `BaseUrl::isRelative($url)` method in `yii\helpers\BaseUrl` (ggh2e3)
 - Bug #18469: Fixed `Link::serialize(array $links)` method in `yii\web\Link` (ggh2e3)
 - Bug #20040: Fix type `boolean` in `MSSQL` (terabytesoftw)
diff --git a/framework/helpers/BaseUrl.php b/framework/helpers/BaseUrl.php
index dcbab192730..864dbc63c48 100644
--- a/framework/helpers/BaseUrl.php
+++ b/framework/helpers/BaseUrl.php
@@ -378,8 +378,7 @@ public static function home($scheme = false)
      */
     public static function isRelative($url)
     {
-        $urlComponents = parse_url($url, PHP_URL_SCHEME);
-        return strncmp($url, '//', 2) && empty($urlComponents);
+        return preg_match('~^[[:alpha:]][[:alnum:]+-.]*://|^//~', $url) === 0;
     }
 
     /**