diff --git a/apps/advanced/common/config/main.php b/apps/advanced/common/config/main.php
index 67d498292d..c9071d108a 100644
--- a/apps/advanced/common/config/main.php
+++ b/apps/advanced/common/config/main.php
@@ -1,7 +1,6 @@
 <?php
 return [
     'vendorPath' => dirname(dirname(__DIR__)) . '/vendor',
-    'extensions' => require(__DIR__ . '/../../vendor/yiisoft/extensions.php'),
     'components' => [
         'cache' => [
             'class' => 'yii\caching\FileCache',
diff --git a/apps/basic/config/console.php b/apps/basic/config/console.php
index 462f35bd6c..85297b3cb1 100644
--- a/apps/basic/config/console.php
+++ b/apps/basic/config/console.php
@@ -10,7 +10,6 @@ return [
     'basePath' => dirname(__DIR__),
     'bootstrap' => ['log'],
     'controllerNamespace' => 'app\commands',
-    'extensions' => require(__DIR__ . '/../vendor/yiisoft/extensions.php'),
     'components' => [
         'cache' => [
             'class' => 'yii\caching\FileCache',
diff --git a/apps/basic/config/web.php b/apps/basic/config/web.php
index fbb7934e82..f9013d8fbb 100644
--- a/apps/basic/config/web.php
+++ b/apps/basic/config/web.php
@@ -6,7 +6,6 @@ $config = [
     'id' => 'basic',
     'basePath' => dirname(__DIR__),
     'bootstrap' => ['log'],
-    'extensions' => require(__DIR__ . '/../vendor/yiisoft/extensions.php'),
     'components' => [
         'cache' => [
             'class' => 'yii\caching\FileCache',
diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 9cc7aac696..477d6b9417 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -56,6 +56,7 @@ Yii Framework 2 Change Log
 - Enh #3472: Added configurable option to encode spaces in dropDownLists and listBoxes (kartik-v)
 - Enh #3518: `yii\helpers\Html::encode()` now replaces invalid code sequences with "?" (DaSourcerer)
 - Enh #3521: Added `yii\filters\HttpCache::sessionCacheLimiter` (qiangxue)
+- Enh #3542: Removed requirement to specify `extensions` in application config (samdark)
 - Enh #3574: Add integrity check support for SQLite (zeeke)
 - Enh: Added support for using sub-queries when building a DB query with `IN` condition (qiangxue)
 - Enh: Supported adding a new response formatter without the need to reconfigure existing formatters (qiangxue)
diff --git a/framework/base/Application.php b/framework/base/Application.php
index 58acc5f20d..0e393d24ff 100644
--- a/framework/base/Application.php
+++ b/framework/base/Application.php
@@ -151,8 +151,11 @@ abstract class Application extends Module
      * The "bootstrap" class listed above will be instantiated during the application
      * [[bootstrap()|bootstrapping process]]. If the class implements [[BootstrapInterface]],
      * its [[BootstrapInterface::bootstrap()|bootstrap()]] method will be also be called.
+     *
+     * If not set explicitily in the application config, this property will be populated with the contents of
+     * `@vendor/yiisoft/extensions.php`.
      */
-    public $extensions = [];
+    public $extensions;
     /**
      * @var array list of components that should be run during the application [[bootstrap()|bootstrapping process]].
      *
@@ -262,6 +265,10 @@ abstract class Application extends Module
      */
     protected function bootstrap()
     {
+        if ($this->extensions === null) {
+            $file = Yii::getAlias('@vendor/yiisoft/extensions.php');
+            $this->extensions = is_file($file) ? include($file) : [];
+        }
         foreach ($this->extensions as $extension) {
             if (!empty($extension['alias'])) {
                 foreach ($extension['alias'] as $name => $path) {