diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index af144a0f3..0671f8970 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -27,6 +27,7 @@ jobs:
           - "7.2"
           - "7.3"
           - "7.4"
+          - "8.0"
           
     steps:
       - name: Checkout
@@ -72,7 +73,7 @@ jobs:
           restore-keys: |
             php${{ matrix.php }}-composer-${{ matrix.dependencies }}-
 
-      - name: Install dependencies with composer php PHP [5.6 - 7.4]
+      - name: Install dependencies with composer php PHP [5.6 - 8.0]
         run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ansi
 
       - name: Run tests with codeception
diff --git a/assets/AppAsset.php b/assets/AppAsset.php
index 47932b165..3b950fe7d 100644
--- a/assets/AppAsset.php
+++ b/assets/AppAsset.php
@@ -26,6 +26,6 @@ class AppAsset extends AssetBundle
     ];
     public $depends = [
         'yii\web\YiiAsset',
-        'yii\bootstrap\BootstrapAsset',
+        'yii\bootstrap4\BootstrapAsset',
     ];
 }
diff --git a/composer.json b/composer.json
index 1375c0105..e3068b065 100644
--- a/composer.json
+++ b/composer.json
@@ -16,7 +16,7 @@
     "require": {
         "php": ">=5.6.0",
         "yiisoft/yii2": "~2.0.14",
-        "yiisoft/yii2-bootstrap": "~2.0.0",
+        "yiisoft/yii2-bootstrap4": "~2.0.0",
         "yiisoft/yii2-swiftmailer": "~2.0.0 || ~2.1.0"
     },
     "require-dev": {
diff --git a/views/layouts/main.php b/views/layouts/main.php
index 87dfdcbc9..54d139995 100644
--- a/views/layouts/main.php
+++ b/views/layouts/main.php
@@ -3,40 +3,39 @@
 /* @var $this \yii\web\View */
 /* @var $content string */
 
-use app\widgets\Alert;
-use yii\helpers\Html;
-use yii\bootstrap\Nav;
-use yii\bootstrap\NavBar;
-use yii\widgets\Breadcrumbs;
 use app\assets\AppAsset;
+use app\widgets\Alert;
+use yii\bootstrap4\Breadcrumbs;
+use yii\bootstrap4\Html;
+use yii\bootstrap4\Nav;
+use yii\bootstrap4\NavBar;
 
 AppAsset::register($this);
 ?>
 <?php $this->beginPage() ?>
 <!DOCTYPE html>
-<html lang="<?= Yii::$app->language ?>">
+<html lang="<?= Yii::$app->language ?>" class="h-100">
 <head>
     <meta charset="<?= Yii::$app->charset ?>">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
     <?php $this->registerCsrfMetaTags() ?>
     <title><?= Html::encode($this->title) ?></title>
     <?php $this->head() ?>
 </head>
-<body>
+<body class="d-flex flex-column h-100">
 <?php $this->beginBody() ?>
 
-<div class="wrap">
+<header>
     <?php
     NavBar::begin([
         'brandLabel' => Yii::$app->name,
         'brandUrl' => Yii::$app->homeUrl,
         'options' => [
-            'class' => 'navbar-inverse navbar-fixed-top',
+            'class' => 'navbar navbar-expand-md navbar-dark bg-dark fixed-top',
         ],
     ]);
     echo Nav::widget([
-        'options' => ['class' => 'navbar-nav navbar-right'],
+        'options' => ['class' => 'navbar-nav'],
         'items' => [
             ['label' => 'Home', 'url' => ['/site/index']],
             ['label' => 'About', 'url' => ['/site/about']],
@@ -45,7 +44,7 @@
                 ['label' => 'Login', 'url' => ['/site/login']]
             ) : (
                 '<li>'
-                . Html::beginForm(['/site/logout'], 'post')
+                . Html::beginForm(['/site/logout'], 'post', ['class' => 'form-inline'])
                 . Html::submitButton(
                     'Logout (' . Yii::$app->user->identity->username . ')',
                     ['class' => 'btn btn-link logout']
@@ -57,7 +56,9 @@
     ]);
     NavBar::end();
     ?>
+</header>
 
+<main role="main" class="flex-shrink-0">
     <div class="container">
         <?= Breadcrumbs::widget([
             'links' => isset($this->params['breadcrumbs']) ? $this->params['breadcrumbs'] : [],
@@ -65,13 +66,12 @@
         <?= Alert::widget() ?>
         <?= $content ?>
     </div>
-</div>
+</main>
 
-<footer class="footer">
+<footer class="footer mt-auto py-3 text-muted">
     <div class="container">
-        <p class="pull-left">&copy; My Company <?= date('Y') ?></p>
-
-        <p class="pull-right"><?= Yii::powered() ?></p>
+        <p class="float-left">&copy; My Company <?= date('Y') ?></p>
+        <p class="float-right"><?= Yii::powered() ?></p>
     </div>
 </footer>
 
diff --git a/views/site/contact.php b/views/site/contact.php
index f4c1e74a2..cf30f7f18 100644
--- a/views/site/contact.php
+++ b/views/site/contact.php
@@ -1,11 +1,11 @@
 <?php
 
 /* @var $this yii\web\View */
-/* @var $form yii\bootstrap\ActiveForm */
+/* @var $form yii\bootstrap4\ActiveForm */
 /* @var $model app\models\ContactForm */
 
-use yii\helpers\Html;
-use yii\bootstrap\ActiveForm;
+use yii\bootstrap4\ActiveForm;
+use yii\bootstrap4\Html;
 use yii\captcha\Captcha;
 
 $this->title = 'Contact';
diff --git a/views/site/index.php b/views/site/index.php
index f78061088..67c98b137 100644
--- a/views/site/index.php
+++ b/views/site/index.php
@@ -6,8 +6,8 @@
 ?>
 <div class="site-index">
 
-    <div class="jumbotron">
-        <h1>Congratulations!</h1>
+    <div class="jumbotron text-center bg-transparent">
+        <h1 class="display-4">Congratulations!</h1>
 
         <p class="lead">You have successfully created your Yii-powered application.</p>
 
@@ -25,7 +25,7 @@
                     ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu
                     fugiat nulla pariatur.</p>
 
-                <p><a class="btn btn-default" href="http://www.yiiframework.com/doc/">Yii Documentation &raquo;</a></p>
+                <p><a class="btn btn-outline-secondary" href="http://www.yiiframework.com/doc/">Yii Documentation &raquo;</a></p>
             </div>
             <div class="col-lg-4">
                 <h2>Heading</h2>
@@ -35,7 +35,7 @@
                     ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu
                     fugiat nulla pariatur.</p>
 
-                <p><a class="btn btn-default" href="http://www.yiiframework.com/forum/">Yii Forum &raquo;</a></p>
+                <p><a class="btn btn-outline-secondary" href="http://www.yiiframework.com/forum/">Yii Forum &raquo;</a></p>
             </div>
             <div class="col-lg-4">
                 <h2>Heading</h2>
@@ -45,7 +45,7 @@
                     ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu
                     fugiat nulla pariatur.</p>
 
-                <p><a class="btn btn-default" href="http://www.yiiframework.com/extensions/">Yii Extensions &raquo;</a></p>
+                <p><a class="btn btn-outline-secondary" href="http://www.yiiframework.com/extensions/">Yii Extensions &raquo;</a></p>
             </div>
         </div>
 
diff --git a/views/site/login.php b/views/site/login.php
index 0944d37e4..8104ff130 100644
--- a/views/site/login.php
+++ b/views/site/login.php
@@ -1,11 +1,11 @@
 <?php
 
 /* @var $this yii\web\View */
-/* @var $form yii\bootstrap\ActiveForm */
+/* @var $form yii\bootstrap4\ActiveForm */
 /* @var $model app\models\LoginForm */
 
-use yii\helpers\Html;
-use yii\bootstrap\ActiveForm;
+use yii\bootstrap4\ActiveForm;
+use yii\bootstrap4\Html;
 
 $this->title = 'Login';
 $this->params['breadcrumbs'][] = $this->title;
@@ -20,7 +20,7 @@
         'layout' => 'horizontal',
         'fieldConfig' => [
             'template' => "{label}\n<div class=\"col-lg-3\">{input}</div>\n<div class=\"col-lg-8\">{error}</div>",
-            'labelOptions' => ['class' => 'col-lg-1 control-label'],
+            'labelOptions' => ['class' => 'col-lg-1 col-form-label'],
         ],
     ]); ?>
 
@@ -29,18 +29,18 @@
         <?= $form->field($model, 'password')->passwordInput() ?>
 
         <?= $form->field($model, 'rememberMe')->checkbox([
-            'template' => "<div class=\"col-lg-offset-1 col-lg-3\">{input} {label}</div>\n<div class=\"col-lg-8\">{error}</div>",
+            'template' => "<div class=\"offset-lg-1 col-lg-3 custom-control custom-checkbox\">{input} {label}</div>\n<div class=\"col-lg-8\">{error}</div>",
         ]) ?>
 
         <div class="form-group">
-            <div class="col-lg-offset-1 col-lg-11">
+            <div class="offset-lg-1 col-lg-11">
                 <?= Html::submitButton('Login', ['class' => 'btn btn-primary', 'name' => 'login-button']) ?>
             </div>
         </div>
 
     <?php ActiveForm::end(); ?>
 
-    <div class="col-lg-offset-1" style="color:#999;">
+    <div class="offset-lg-1" style="color:#999;">
         You may login with <strong>admin/admin</strong> or <strong>demo/demo</strong>.<br>
         To modify the username/password, please check out the code <code>app\models\User::$users</code>.
     </div>
diff --git a/web/css/site.css b/web/css/site.css
index 2bfebd275..cd81ae1c9 100644
--- a/web/css/site.css
+++ b/web/css/site.css
@@ -1,34 +1,16 @@
-html,
-body {
-    height: 100%;
-}
-
-.wrap {
-    min-height: 100%;
-    height: auto;
-    margin: 0 auto -60px;
-    padding: 0 0 60px;
-}
-
-.wrap > .container {
+main > .container {
     padding: 70px 15px 20px;
 }
 
 .footer {
-    height: 60px;
     background-color: #f5f5f5;
-    border-top: 1px solid #ddd;
-    padding-top: 20px;
-}
-
-.jumbotron {
-    text-align: center;
-    background-color: transparent;
+    font-size: .9em;
+    height: 60px;
 }
 
-.jumbotron .btn {
-    font-size: 21px;
-    padding: 14px 24px;
+.footer > .container {
+    padding-right: 15px;
+    padding-left: 15px;
 }
 
 .not-set {
@@ -38,38 +20,24 @@ body {
 
 /* add sorting icons to gridview sort links */
 a.asc:after, a.desc:after {
-    position: relative;
-    top: 1px;
+    content: '';
+    left: 3px;
     display: inline-block;
-    font-family: 'Glyphicons Halflings';
-    font-style: normal;
-    font-weight: normal;
-    line-height: 1;
-    padding-left: 5px;
+    width: 0;
+    height: 0;
+    border: solid 5px transparent;
+    margin: 4px 4px 2px 4px;
+    background: transparent;
 }
 
 a.asc:after {
-    content: /*"\e113"*/ "\e151";
+    border-bottom: solid 7px #212529;
+    border-top-width: 0;
 }
 
 a.desc:after {
-    content: /*"\e114"*/ "\e152";
-}
-
-.sort-numerical a.asc:after {
-    content: "\e153";
-}
-
-.sort-numerical a.desc:after {
-    content: "\e154";
-}
-
-.sort-ordinal a.asc:after {
-    content: "\e155";
-}
-
-.sort-ordinal a.desc:after {
-    content: "\e156";
+    border-top: solid 7px #212529;
+    border-bottom-width: 0;
 }
 
 .grid-view th {
@@ -92,8 +60,8 @@ a.desc:after {
 
 /* align the logout "link" (button in form) of the navbar */
 .nav li > form > button.logout {
-    padding: 15px;
-    border: none;
+    padding-top: 7px;
+    color: rgba(255, 255, 255, 0.5);
 }
 
 @media(max-width:767px) {
@@ -101,13 +69,14 @@ a.desc:after {
         display:block;
         text-align: left;
         width: 100%;
-        padding: 10px 15px;
+        padding: 10px 0;
     }
 }
 
 .nav > li > form > button.logout:focus,
 .nav > li > form > button.logout:hover {
     text-decoration: none;
+    color: rgba(255, 255, 255, 0.75);
 }
 
 .nav > li > form > button.logout:focus {
diff --git a/widgets/Alert.php b/widgets/Alert.php
index ae6c1d85c..9fbc73939 100644
--- a/widgets/Alert.php
+++ b/widgets/Alert.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace app\widgets;
 
 use Yii;
@@ -22,7 +23,7 @@
  * @author Kartik Visweswaran <kartikv2@gmail.com>
  * @author Alexander Makarov <sam@rmcreative.ru>
  */
-class Alert extends \yii\bootstrap\Widget
+class Alert extends \yii\bootstrap4\Widget
 {
     /**
      * @var array the alert types configuration for the flash messages.
@@ -59,7 +60,7 @@ public function run()
             }
 
             foreach ((array) $flash as $i => $message) {
-                echo \yii\bootstrap\Alert::widget([
+                echo \yii\bootstrap4\Alert::widget([
                     'body' => $message,
                     'closeButton' => $this->closeButton,
                     'options' => array_merge($this->options, [
