diff --git a/extensions/apidoc/commands/RenderController.php b/extensions/apidoc/commands/RenderController.php
index d6ae80f970..3c676e1da8 100644
--- a/extensions/apidoc/commands/RenderController.php
+++ b/extensions/apidoc/commands/RenderController.php
@@ -128,7 +128,7 @@ class RenderController extends Controller
 		return new $rendererClass();
 	}
 
-	protected function findFiles($path, $except = ['/vendor/', '/tests/'])
+	protected function findFiles($path, $except = ['vendor/', 'tests/'])
 	{
 		$path = FileHelper::normalizePath($path);
 		$options = [
diff --git a/extensions/apidoc/templates/bootstrap/Renderer.php b/extensions/apidoc/templates/bootstrap/Renderer.php
index b40426dd5b..ef8d37b45a 100644
--- a/extensions/apidoc/templates/bootstrap/Renderer.php
+++ b/extensions/apidoc/templates/bootstrap/Renderer.php
@@ -28,6 +28,103 @@ class Renderer extends \yii\apidoc\templates\html\Renderer
 
 	public $guideUrl;
 
+	public $extensions = [
+		'apidoc',
+		'authclient',
+		'bootstrap',
+		'codeception',
+		'composer',
+		'debug',
+		'elasticsearch',
+		'faker',
+		'gii',
+		'imagine',
+		'jui',
+		'mongodb',
+		'redis',
+		'smarty',
+		'sphinx',
+		'swiftmailer',
+		'twig',
+	];
+
+	/**
+	 * Renders a given [[Context]].
+	 *
+	 * @param Context $context the api documentation context to render.
+	 * @param Controller $controller the apidoc controller instance. Can be used to control output.
+	 */
+	public function renderApi($context, $controller)
+	{
+		parent::renderApi($context, $controller);
+		$dir = Yii::getAlias($this->targetDir);
+		$types = array_merge($context->classes, $context->interfaces, $context->traits);
+
+		$controller->stdout('generating extension index files...');
+		foreach($this->extensions as $ext) {
+			$readme = @file_get_contents("https://raw.github.com/yiisoft/yii2-$ext/master/README.md");
+			$indexFileContent = $this->renderWithLayout($this->indexView, [
+				'docContext' => $context,
+				'types' => $this->filterTypes($types, $ext),
+				'readme' => $readme ?: null,
+			]);
+			file_put_contents($dir . "/ext_{$ext}_index.html", $indexFileContent);
+		}
+		$controller->stdout('done.' . PHP_EOL, Console::FG_GREEN);
+	}
+
+	public function getNavTypes($type, $types)
+	{
+		if ($type === null) {
+			return $types;
+		}
+		$extensions = $this->extensions;
+		$navClasses = 'app';
+		if (isset($type)) {
+			if ($type->name == 'Yii') {
+				$navClasses = 'yii';
+			} elseif (strncmp($type->name, 'yii\\', 4) == 0) {
+				$subName = substr($type->name, 4);
+				if (($pos = strpos($subName, '\\')) !== false) {
+					$subNamespace = substr($subName, 0, $pos);
+					if (in_array($subNamespace, $extensions)) {
+						$navClasses = $subNamespace;
+					} else {
+						$navClasses = 'yii';
+					}
+				}
+			}
+		}
+		return $this->filterTypes($types, $navClasses);
+	}
+
+	protected function filterTypes($types, $navClasses)
+	{
+		switch ($navClasses)
+		{
+			case 'app':
+				$types = array_filter($types, function($val) {
+					return strncmp($val->name, 'yii\\', 4) !== 0;
+				});
+				break;
+			case 'yii':
+				$self = $this;
+				$types = array_filter($types, function($val) use ($self) {
+					if (strlen($val->name) < 5) {
+						return false;
+					}
+					$subName = substr($val->name, 4, strpos($val->name, '\\', 5) - 4);
+					return strncmp($val->name, 'yii\\', 4) === 0 && !in_array($subName, $self->extensions);
+				});
+				break;
+			default:
+				$types = array_filter($types, function($val) use ($navClasses) {
+					return strncmp($val->name, "yii\\$navClasses\\", strlen("yii\\$navClasses\\")) === 0;
+				});
+		}
+		return $types;
+	}
+
 	/**
 	 * Renders a given [[Context]].
 	 *
diff --git a/extensions/apidoc/templates/bootstrap/layouts/api.php b/extensions/apidoc/templates/bootstrap/layouts/api.php
index 157e7fdb3e..935705d590 100644
--- a/extensions/apidoc/templates/bootstrap/layouts/api.php
+++ b/extensions/apidoc/templates/bootstrap/layouts/api.php
@@ -11,6 +11,7 @@ $this->beginContent('@yii/apidoc/templates/bootstrap/layouts/main.php'); ?>
 <div class="row">
 	<div class="col-md-2">
 		<?php
+		$types = $this->context->getNavTypes(isset($type) ? $type : null, $types);
 		ksort($types);
 		$nav = [];
 		foreach($types as $i=>$class) {
diff --git a/extensions/apidoc/templates/bootstrap/layouts/main.php b/extensions/apidoc/templates/bootstrap/layouts/main.php
index 1dca1ddb1f..90708ba986 100644
--- a/extensions/apidoc/templates/bootstrap/layouts/main.php
+++ b/extensions/apidoc/templates/bootstrap/layouts/main.php
@@ -37,9 +37,17 @@ $this->beginPage();
 		'padded' => false,
 		'view' => $this,
 	]);
+	$extItems = [];
+	foreach($this->context->extensions as $ext) {
+		$extItems[] = [
+			'label' => $ext,
+			'url' => "./ext_{$ext}_index.html",
+		];
+	}
 	$nav = [
 		['label' => 'Class reference', 'url' => './index.html'],
 //		['label' => 'Application API', 'url' => '/site/about'],
+		['label' => 'Extensions', 'items' => $extItems],
 	];
 	if ($this->context->guideUrl !== null) {
 		$nav[] = ['label' => 'Guide', 'url' => $this->context->guideUrl . 'guide_index.html'];
diff --git a/extensions/apidoc/templates/bootstrap/views/index.php b/extensions/apidoc/templates/bootstrap/views/index.php
index a8b29fc526..b971b8e9ed 100644
--- a/extensions/apidoc/templates/bootstrap/views/index.php
+++ b/extensions/apidoc/templates/bootstrap/views/index.php
@@ -8,6 +8,10 @@ use yii\apidoc\models\TraitDoc;
  * @var yii\web\View $this
  */
 
+if (isset($readme)) {
+	echo \yii\apidoc\helpers\Markdown::process($readme);
+}
+
 ?><h1>Class Reference</h1>
 
 <table class="summaryTable docIndex table table-bordered table-striped table-hover">