diff --git a/templates/base.html b/templates/base.html
index 2ac9ec9..819fd28 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -32,7 +32,8 @@
             const getTheme = () => {
                 const storedTheme = localStorage.getItem('theme');
                 if (storedTheme) return storedTheme;
-                return window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
+                // For new visitors, default to dark mode regardless of their OS setting.
+                return 'dark';
             };
 
             const setTheme = (theme) => {