diff --git a/_config.yml b/_config.yml
index f6f3080..71b785a 100644
--- a/_config.yml
+++ b/_config.yml
@@ -93,9 +93,9 @@ social:
 
 # Analytics
 analytics:
-  provider               : plausible # false (default), "google", "google-universal", "custom", "plausible"
+  provider               : google # false (default), "google", "google-universal", "custom", "plausible"
   google:
-    tracking_id          : ""
+    tracking_id          : "G-0ZPVV6GNEY"
   plausible:
     domain               : "camilo-cf.github.io"
     api_host             : "https://plausible.io"
diff --git a/_includes/analytics-providers/google.html b/_includes/analytics-providers/google.html
index 57554b6..54f812a 100644
--- a/_includes/analytics-providers/google.html
+++ b/_includes/analytics-providers/google.html
@@ -1,11 +1,20 @@
-<script type="text/javascript">
-  var _gaq = _gaq || [];
-  _gaq.push(['_setAccount', '{{ site.analytics.google.tracking_id }}']);
-  _gaq.push(['_trackPageview']);
-
-  (function() {
-    var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
-    ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
-    var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
-  })();
-</script>
+<!-- Google Analytics 4 (GA4) -->
+<!-- Note: When consent banner is enabled, consent.js handles GA4 loading after user consent -->
+{% if site.analytics.google.tracking_id %}
+  {% unless site.consent_banner.enabled %}
+    <!-- Consent banner disabled: Load GA4 directly -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id={{ site.analytics.google.tracking_id }}"></script>
+    <script>
+      window.dataLayer = window.dataLayer || [];
+      function gtag(){dataLayer.push(arguments);}
+      gtag('js', new Date());
+      gtag('config', '{{ site.analytics.google.tracking_id }}');
+    </script>
+  {% else %}
+    <!-- Consent banner enabled: Setup handled by consent.js -->
+    <script>
+      window.dataLayer = window.dataLayer || [];
+      window.gtag = window.gtag || function(){dataLayer.push(arguments);};
+    </script>
+  {% endunless %}
+{% endif %}
diff --git a/_includes/head/custom.html b/_includes/head/custom.html
index fee5d30..cc89989 100644
--- a/_includes/head/custom.html
+++ b/_includes/head/custom.html
@@ -2,6 +2,12 @@
 
 <!-- start custom head snippets -->
 
+<!-- Security Headers -->
+<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' 'unsafe-inline' https://www.googletagmanager.com https://cdnjs.cloudflare.com https://giscus.app https://cdn.jsdelivr.net; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; connect-src 'self' https://www.google-analytics.com https://giscus.app https://api.github.com; frame-src https://giscus.app; font-src 'self' data:; object-src 'none'; base-uri 'self'; form-action 'self';">
+<meta http-equiv="X-Content-Type-Options" content="nosniff">
+<meta http-equiv="Referrer-Policy" content="strict-origin-when-cross-origin">
+<meta http-equiv="Permissions-Policy" content="geolocation=(), microphone=(), camera=(), payment=(), usb=(), magnetometer=(), gyroscope=(), accelerometer=()">
+
 <link rel="apple-touch-icon" sizes="57x57" href="{{ base_path }}/images/apple-touch-icon-57x57.png?v=M44lzPylqQ">
 <link rel="apple-touch-icon" sizes="60x60" href="{{ base_path }}/images/apple-touch-icon-60x60.png?v=M44lzPylqQ">
 <link rel="apple-touch-icon" sizes="72x72" href="{{ base_path }}/images/apple-touch-icon-72x72.png?v=M44lzPylqQ">
@@ -24,15 +30,22 @@
 <meta name="theme-color" content="#ffffff">
 <link rel="stylesheet" href="{{ base_path }}/assets/css/academicons.css"/>
 
-<script type="text/x-mathjax-config"> MathJax.Hub.Config({ TeX: { equationNumbers: { autoNumber: "all" } } }); </script>
-<script type="text/x-mathjax-config">
-  MathJax.Hub.Config({
-    tex2jax: {
-      inlineMath: [ ['$','$'], ["\\(","\\)"] ],
-      processEscapes: true
+<!-- MathJax 3 Configuration -->
+<script>
+  window.MathJax = {
+    tex: {
+      inlineMath: [['$', '$'], ['\\(', '\\)']],
+      displayMath: [['$$', '$$'], ['\\[', '\\]']],
+      processEscapes: true,
+      tags: 'ams'
+    },
+    options: {
+      skipHtmlTags: ['script', 'noscript', 'style', 'textarea', 'pre']
     }
-  });
+  };
 </script>
-<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"></script>
+<script src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"
+        integrity="sha256-3Fdoa0sH4Qndroe1Y6nAUOervFPNCvFhUcHfCKN69sQ="
+        crossorigin="anonymous"></script>
 
 <!-- end custom head snippets -->