diff --git a/404.html b/404.html
index fe369a8..21fbe07 100644
--- a/404.html
+++ b/404.html
@@ -39,6 +39,15 @@
             background-color: #f8f8f8;
         }
     </style>
+    <!-- Google tag (gtag.js) -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-9NPSN4RVS4"></script>
+    <script>
+        window.dataLayer = window.dataLayer || [];
+        function gtag(){dataLayer.push(arguments);}
+        gtag('js', new Date());
+
+        gtag('config', 'G-9NPSN4RVS4');
+    </script>
 </head>
 <body>
 <div class="error-container">
diff --git a/index.html b/index.html
index 1969989..2c50146 100644
--- a/index.html
+++ b/index.html
@@ -31,6 +31,15 @@
     <link rel="stylesheet" href="src/css/style.css" />
     <script src="src/js/script.js" defer></script>
     <link rel="icon" type="image/x-icon" href="images/favicon.ico">
+    <!-- Google tag (gtag.js) -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-9NPSN4RVS4"></script>
+    <script>
+        window.dataLayer = window.dataLayer || [];
+        function gtag(){dataLayer.push(arguments);}
+        gtag('js', new Date());
+
+        gtag('config', 'G-9NPSN4RVS4');
+    </script>
 </head>
 
 <body>
diff --git a/src/html/about.html b/src/html/about.html
index 7b3cfee..02ddaf0 100644
--- a/src/html/about.html
+++ b/src/html/about.html
@@ -7,6 +7,15 @@
     <link rel="stylesheet" href="../css/style.css">
     <link rel="icon" type="image/x-icon" href="../../images/favicon.ico">
     <link rel="manifest" href="../../manifest.json">
+    <!-- Google tag (gtag.js) -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-9NPSN4RVS4"></script>
+    <script>
+        window.dataLayer = window.dataLayer || [];
+        function gtag(){dataLayer.push(arguments);}
+        gtag('js', new Date());
+
+        gtag('config', 'G-9NPSN4RVS4');
+    </script>
 </head>
 
 <body style="background-image: url(../../images/snow.jpg)">
