diff --git a/_includes/head.html b/_includes/head.html
index c81f6cb..eb3ffd3 100644
--- a/_includes/head.html
+++ b/_includes/head.html
@@ -102,7 +102,7 @@
       });
     }
   </script>
-
+{% if jekyll.environment == 'production' and site.google_analytics.id != empty and site.google_analytics.id %}
   <!-- Google Tag Manager -->
 <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
   new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
@@ -110,6 +110,7 @@
   'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
   })(window,document,'script','dataLayer','GTM-W4PKSB86');</script>
   <!-- End Google Tag Manager -->
+{% endif %}
 
   {% unless site.theme_mode %}
   {% include mode-toggle.html %}
diff --git a/_layouts/default.html b/_layouts/default.html
index 0946935..0854db1 100644
--- a/_layouts/default.html
+++ b/_layouts/default.html
@@ -10,73 +10,64 @@ layout: compress
 {% include lang.html %}
 
 {% capture prefer_mode %}
-  {% if site.theme_mode %}
-    data-mode="{{ site.theme_mode }}"
-  {% endif %}
+{% if site.theme_mode %}
+data-mode="{{ site.theme_mode }}"
+{% endif %}
 {% endcapture %}
 
 <!-- `site.alt_lang` can specify a language different from the UI -->
 <html lang="{{ site.alt_lang | default: site.lang }}" {{ prefer_mode }}>
-  {% include head.html %}
+{% include head.html %}
 
-  <body>
-    
-    <!-- Google Tag Manager (noscript) -->
-<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-W4PKSB86"
-  height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
+<body>
+
+  {% if jekyll.environment == 'production' and site.google_analytics.id != empty and site.google_analytics.id %}
+  <!-- Google Tag Manager (noscript) -->
+  <noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-W4PKSB86" height="0" width="0"
+      style="display:none;visibility:hidden"></iframe></noscript>
   <!-- End Google Tag Manager (noscript) -->
+  {% endif %}
+  
+  {% include sidebar.html lang=lang %}
 
-    {% include sidebar.html lang=lang %}
-
-    <div id="main-wrapper" class="d-flex justify-content-center">
-      <div id="main" class="container px-xxl-5">
-        {% include topbar.html lang=lang %}
-        {{ content }}
-        {% include_cached search-results.html lang=lang %}
-      </div>
+  <div id="main-wrapper" class="d-flex justify-content-center">
+    <div id="main" class="container px-xxl-5">
+      {% include topbar.html lang=lang %}
+      {{ content }}
+      {% include_cached search-results.html lang=lang %}
     </div>
+  </div>
 
-    {% include_cached footer.html lang=lang %}
+  {% include_cached footer.html lang=lang %}
 
-    <div id="mask"></div>
+  <div id="mask"></div>
 
-    <button id="back-to-top" aria-label="back-to-top" class="btn btn-lg btn-box-shadow">
-      <i class="fas fa-angle-up"></i>
-    </button>
+  <button id="back-to-top" aria-label="back-to-top" class="btn btn-lg btn-box-shadow">
+    <i class="fas fa-angle-up"></i>
+  </button>
 
-    {% if site.pwa.enabled %}
-      <div
-        id="notification"
-        class="toast"
-        role="alert"
-        aria-live="assertive"
-        aria-atomic="true"
-        data-bs-animation="true"
-        data-bs-autohide="false"
-      >
-        <div class="toast-header">
-          <button
-            type="button"
-            class="btn-close ms-auto"
-            data-bs-dismiss="toast"
-            aria-label="Close"
-          ></button>
-        </div>
-        <div class="toast-body text-center pt-0">
-          <p class="px-2 mb-3">{{ site.data.locales[lang].notification.update_found }}</p>
-          <button type="button" class="btn btn-primary" aria-label="Update">
-            {{ site.data.locales[lang].notification.update }}
-          </button>
-        </div>
-      </div>
-    {% endif %}
+  {% if site.pwa.enabled %}
+  <div id="notification" class="toast" role="alert" aria-live="assertive" aria-atomic="true" data-bs-animation="true"
+    data-bs-autohide="false">
+    <div class="toast-header">
+      <button type="button" class="btn-close ms-auto" data-bs-dismiss="toast" aria-label="Close"></button>
+    </div>
+    <div class="toast-body text-center pt-0">
+      <p class="px-2 mb-3">{{ site.data.locales[lang].notification.update_found }}</p>
+      <button type="button" class="btn btn-primary" aria-label="Update">
+        {{ site.data.locales[lang].notification.update }}
+      </button>
+    </div>
+  </div>
+  {% endif %}
 
-    {% include js-selector.html %}
+  {% include js-selector.html %}
 
-    {% if page.mermaid %}
-      {% include mermaid.html %}
-    {% endif %}
+  {% if page.mermaid %}
+  {% include mermaid.html %}
+  {% endif %}
 
-    {% include_cached search-loader.html %}
-  </body>
-</html>
+  {% include_cached search-loader.html %}
+</body>
+
+</html>
\ No newline at end of file
