diff --git a/cron.php b/cron.php
index 2a398d3..683f605 100644
--- a/cron.php
+++ b/cron.php
@@ -1,6 +1,10 @@
 <?php
 namespace YTKNS;
 
+// Prevent running cron script during maintenance
+if(YTKNS_MAINTENANCE)
+    return;
+
 if(!defined('YTKNS_SEM_NAME'))
     define('YTKNS_SEM_NAME', 'b');
 if(!defined('YTKNS_SFM_PATH'))
diff --git a/public/assets/style.css b/public/assets/style.css
index 99d2802..f5d8c1c 100644
--- a/public/assets/style.css
+++ b/public/assets/style.css
@@ -45,6 +45,13 @@ body {
     box-shadow: 0 1px 4px #000;
 }
 
+.maintenance {
+    background: #c00;
+    color: #fff;
+    font-size: .9em;
+    padding: 5px 10px;
+}
+
 @media(min-width: 1000px) {
     body { padding-top: 1px; }
     .wrapper { margin: 3px auto 10px; }
diff --git a/public/index.php b/public/index.php
index c794540..16a81af 100644
--- a/public/index.php
+++ b/public/index.php
@@ -68,6 +68,8 @@ function html_header(array $vars = []): string {
 
     $vars['menu_user'] = Template::renderSet('menu-user-item', $userMenu);
 
+    $vars['maintenance'] = YTKNS_MAINTENANCE ? Template::renderRaw('maintenance') : '';
+
     return Template::renderRaw('header', $vars);
 }
 
@@ -117,7 +119,7 @@ function html_pagination(int $pages, int $current, string $urlFormat): string {
     return $html . '</div>';
 }
 
-if(!empty($_COOKIE['ytkns_login']) && is_string($_COOKIE['ytkns_login'])) {
+if(!YTKNS_MAINTENANCE && !empty($_COOKIE['ytkns_login']) && is_string($_COOKIE['ytkns_login'])) {
     try {
         $session = UserSession::byToken($_COOKIE['ytkns_login']);
         $session->update();
@@ -152,13 +154,15 @@ if(!empty($zoneName)) {
         return;
     }
 
-    if(!empty($_GET['_refresh_screenshot'])) {
-        header('Location: /');
-        $zoneInfo->takeScreenshot();
-        return;
-    }
+    if(!YTKNS_MAINTENANCE) {
+        if(!empty($_GET['_refresh_screenshot'])) {
+            header('Location: /');
+            $zoneInfo->takeScreenshot();
+            return;
+        }
 
-    ZoneView::increment($zoneInfo, $_SERVER['REMOTE_ADDR']);
+        ZoneView::increment($zoneInfo, $_SERVER['REMOTE_ADDR']);
+    }
 
     echo (string)$zoneInfo->getPageBuilder(true);
     return;
@@ -924,6 +928,12 @@ if($reqPath === '/settings/invites') {
 }
 
 if($reqPath === '/auth/login') {
+    if(YTKNS_MAINTENANCE) {
+        http_response_code(503);
+        echo html_information('You cannot log in during maintenance.');
+        return;
+    }
+
     if(UserSession::hasInstance()) {
         http_response_code(404);
         echo html_information('You are logged in already.');
@@ -985,6 +995,12 @@ if($reqPath === '/auth/login') {
 }
 
 if($reqPath === '/auth/register') {
+    if(YTKNS_MAINTENANCE) {
+        http_response_code(503);
+        echo html_information('You cannot register during maintenance.');
+        return;
+    }
+
     if(UserSession::hasInstance()) {
         http_response_code(404);
         echo html_information('You are logged in already.');
diff --git a/src/Config.php b/src/Config.php
index 4cb0216..313a117 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -39,7 +39,7 @@ final class Config {
     public static function set(string $key, $value, bool $soft = false): void {
         self::$config[$key] = $value;
 
-        if(!$soft) {
+        if(!YTKNS_MAINTENANCE && !$soft) {
             $value = serialize($value);
 
             $save = DB::prepare('REPLACE INTO `ytkns_config` (`config_key`, `config_value`) VALUES (:key, :value)');
diff --git a/templates/header.html b/templates/header.html
index e3c31e8..4d917dd 100644
--- a/templates/header.html
+++ b/templates/header.html
@@ -22,6 +22,7 @@
     </head>
     <body>
         <div class="wrapper">
+            :maintenance
             <div class="header">
                 <div class="header-usermenu">
                     :menu_user
diff --git a/templates/maintenance.html b/templates/maintenance.html
new file mode 100644
index 0000000..bb66733
--- /dev/null
+++ b/templates/maintenance.html
@@ -0,0 +1,3 @@
+<div class="maintenance">
+    YTKNS is currently in read-only maintenance mode.
+</div>
\ No newline at end of file
