diff --git a/themes/mytheme/layouts/partials/header.html b/themes/mytheme/layouts/partials/header.html
index f54c6ec..6590d11 100644
--- a/themes/mytheme/layouts/partials/header.html
+++ b/themes/mytheme/layouts/partials/header.html
@@ -1,3 +1,45 @@
+
+{{- /* theme-toggle is enabled */}}
+{{- if (not site.Params.disableThemeToggle) }}
+{{- /* theme is light */}}
+{{- if (eq site.Params.defaultTheme "light") }}
+<script>
+    if (localStorage.getItem("pref-theme") === "dark") {
+        document.body.classList.add('dark');
+    }
+
+</script>
+{{- /* theme is dark */}}
+{{- else if (eq site.Params.defaultTheme "dark") }}
+<script>
+    if (localStorage.getItem("pref-theme") === "light") {
+        document.body.classList.remove('dark')
+    }
+
+</script>
+{{- else }}
+{{- /* theme is auto */}}
+<script>
+    if (localStorage.getItem("pref-theme") === "dark") {
+        document.body.classList.add('dark');
+    } else if (localStorage.getItem("pref-theme") === "light") {
+        document.body.classList.remove('dark')
+    } else if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+        document.body.classList.add('dark');
+    }
+
+</script>
+{{- end }}
+{{- /* theme-toggle is disabled and theme is auto */}}
+{{- else if (and (ne site.Params.defaultTheme "light") (ne site.Params.defaultTheme "dark"))}}
+<script>
+    if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+        document.body.classList.add('dark');
+    }
+
+</script>
+{{- end }}
+
 <header class="header">
     <nav class="nav{{- if .IsHome }} nav-home{{- else if (not .IsPage) }} nav-nonpost{{- end }}">
         <div class="logo">