diff --git a/app/cookies/page.tsx b/app/cookies/page.tsx
index 0c341521..c82bbde7 100644
--- a/app/cookies/page.tsx
+++ b/app/cookies/page.tsx
@@ -13,6 +13,7 @@
 import type { Metadata } from "next";
 import Link from "next/link";
 import { site } from "@/content";
+import ThemeToggle from "@/components/ThemeToggle";
 
 const lastUpdated = "2 May 2026";
 
@@ -37,7 +38,7 @@ export default function CookiePolicyPage() {
 
       {/* Lightweight header — just a back-link */}
       <header className="border-b border-[var(--border)]">
-        <div className="mx-auto flex h-20 w-full max-w-3xl items-center px-6 sm:px-8">
+        <div className="mx-auto flex h-20 w-full max-w-3xl items-center justify-between gap-4 px-6 sm:px-8">
           <Link
             href="/"
             className="inline-flex items-center gap-2 text-sm text-[var(--text-soft)] transition-colors hover:text-[var(--text)]"
@@ -45,6 +46,7 @@ export default function CookiePolicyPage() {
             <span aria-hidden="true">←</span>
             Back to Novarix Networks
           </Link>
+          <ThemeToggle />
         </div>
       </header>
 
@@ -78,7 +80,7 @@ export default function CookiePolicyPage() {
               What we store
             </h2>
             <p className="mt-3">
-              We use one small browser storage entry. It is first-party,
+              We use two small browser storage entries. Both are first-party,
               confined to your browser, and never shared with anyone:
             </p>
 
@@ -96,6 +98,21 @@ export default function CookiePolicyPage() {
                   every page. Persists until you clear your browser data.
                 </p>
               </div>
+
+              <div className="rounded-2xl border border-[var(--border)] bg-[var(--surface)] p-5 backdrop-blur sm:p-6">
+                <p className="font-mono text-sm font-semibold text-[var(--text)]">
+                  novarix-theme
+                </p>
+                <p className="mt-2 text-sm">
+                  <span className="font-semibold text-[var(--text)]">
+                    Preference.
+                  </span>{" "}
+                  Stored in <code>localStorage</code>. Remembers whether you
+                  chose light mode or dark mode so the site uses your preferred
+                  theme on future visits. Persists until you clear your browser
+                  data.
+                </p>
+              </div>
             </div>
           </section>
 
diff --git a/app/globals.css b/app/globals.css
index 65b57a42..df08f610 100644
--- a/app/globals.css
+++ b/app/globals.css
@@ -66,8 +66,7 @@
    `@media (prefers-color-scheme: dark)` block.
    --------------------------------------------------------------------------- */
 :root {
-  color-scheme: light dark;
-
+  color-scheme: light;
   --bg: var(--color-ink-50);
   --surface: oklch(1 0 0 / 0.7);
   --surface-strong: oklch(1 0 0 / 0.92);
@@ -85,8 +84,28 @@
   --button-hover: var(--color-ink-800);
 }
 
+:root[data-theme="dark"] {
+  color-scheme: dark;
+  --bg: var(--color-ink-950);
+  --surface: oklch(0.13 0.028 255 / 0.55);
+  --surface-strong: oklch(0.13 0.028 255 / 0.85);
+  --text: var(--color-ink-100);
+  --text-soft: var(--color-ink-400);
+  --border: oklch(1 0 0 / 0.08);
+  --border-strong: oklch(1 0 0 / 0.16);
+  --accent: var(--color-brand-400);
+  --accent-soft: oklch(0.7 0.14 240 / 0.18);
+  --ring: oklch(0.7 0.14 240 / 0.5);
+  --grid: oklch(0.84 0.012 250 / 0.06);
+
+  --button-bg: var(--color-ink-100);
+  --button-fg: var(--color-ink-950);
+  --button-hover: var(--color-ink-50);
+}
+
 @media (prefers-color-scheme: dark) {
-  :root {
+  :root:not([data-theme]) {
+    color-scheme: dark;
     --bg: var(--color-ink-950);
     --surface: oklch(0.13 0.028 255 / 0.55);
     --surface-strong: oklch(0.13 0.028 255 / 0.85);
@@ -218,12 +237,20 @@
   display: none;
 }
 
+:root[data-theme="dark"] .brand-light {
+  display: none;
+}
+
+:root[data-theme="dark"] .brand-dark {
+  display: block;
+}
+
 @media (prefers-color-scheme: dark) {
-  .brand-light {
+  :root:not([data-theme]) .brand-light {
     display: none;
   }
 
-  .brand-dark {
+  :root:not([data-theme]) .brand-dark {
     display: block;
   }
 }
diff --git a/app/layout.tsx b/app/layout.tsx
index a15c36c3..272511de 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -63,6 +63,35 @@ export default function RootLayout({
 }: Readonly<{ children: React.ReactNode }>) {
   return (
     <html lang="en-GB" suppressHydrationWarning>
+      <head>
+        <script
+          dangerouslySetInnerHTML={{
+            __html: `
+              (function () {
+                var key = "novarix-theme";
+                var root = document.documentElement;
+                var theme = "light";
+
+                try {
+                  var saved = window.localStorage.getItem(key);
+                  if (saved === "light" || saved === "dark") {
+                    theme = saved;
+                  } else if (window.matchMedia("(prefers-color-scheme: dark)").matches) {
+                    theme = "dark";
+                  }
+                } catch (error) {
+                  if (window.matchMedia("(prefers-color-scheme: dark)").matches) {
+                    theme = "dark";
+                  }
+                }
+
+                root.dataset.theme = theme;
+                root.style.colorScheme = theme;
+              })();
+            `,
+          }}
+        />
+      </head>
       <body>
         {children}
         <CookieBanner />
diff --git a/app/page.tsx b/app/page.tsx
index 463253ca..4024fa2d 100644
--- a/app/page.tsx
+++ b/app/page.tsx
@@ -27,6 +27,7 @@ import Link from "next/link";
 import React, { useMemo, useState } from "react";
 import { site } from "@/content";
 import { openCookieBanner } from "@/components/CookieBanner";
+import ThemeToggle from "@/components/ThemeToggle";
 
 // Type for the mouse-pointer position used to move the background glow.
 type PointerState = { x: number; y: number };
@@ -212,15 +213,19 @@ export default function HomePage() {
                 Contact
                 <span aria-hidden="true">→</span>
               </a>
+              <ThemeToggle />
             </nav>
 
-            {/* Mobile-only Contact pill — replaces the full nav on small screens */}
-            <a
-              href="#contact"
-              className="inline-flex items-center rounded-full border border-[var(--border-strong)] px-3 py-1.5 text-xs text-[var(--text)] transition-colors hover:border-[var(--accent)] hover:text-[var(--accent)] sm:hidden"
-            >
-              Contact
-            </a>
+            {/* Mobile controls — simplified for smaller screens */}
+            <div className="flex items-center gap-2 sm:hidden">
+              <ThemeToggle className="text-xs" />
+              <a
+                href="#contact"
+                className="inline-flex items-center rounded-full border border-[var(--border-strong)] px-3 py-1.5 text-xs text-[var(--text)] transition-colors hover:border-[var(--accent)] hover:text-[var(--accent)]"
+              >
+                Contact
+              </a>
+            </div>
           </div>
         </header>
 
diff --git a/components/ThemeToggle.tsx b/components/ThemeToggle.tsx
new file mode 100644
index 00000000..21832c41
--- /dev/null
+++ b/components/ThemeToggle.tsx
@@ -0,0 +1,50 @@
+"use client";
+
+import { useLayoutEffect, useState } from "react";
+
+const THEME_KEY = "novarix-theme";
+
+type Theme = "light" | "dark";
+
+function applyTheme(theme: Theme) {
+  document.documentElement.dataset.theme = theme;
+  document.documentElement.style.colorScheme = theme;
+}
+
+export default function ThemeToggle({
+  className = "",
+}: {
+  className?: string;
+}) {
+  const [theme, setTheme] = useState<Theme>("light");
+
+  useLayoutEffect(() => {
+    const current =
+      document.documentElement.dataset.theme === "dark" ? "dark" : "light";
+    setTheme(current);
+  }, []);
+
+  function toggleTheme() {
+    const nextTheme: Theme = theme === "dark" ? "light" : "dark";
+    setTheme(nextTheme);
+    applyTheme(nextTheme);
+
+    try {
+      window.localStorage.setItem(THEME_KEY, nextTheme);
+    } catch {
+      /* storage unavailable — silently ignore */
+    }
+  }
+
+  return (
+    <button
+      type="button"
+      onClick={toggleTheme}
+      aria-label={`Switch to ${theme === "dark" ? "light" : "dark"} mode`}
+      title={`Switch to ${theme === "dark" ? "light" : "dark"} mode`}
+      className={`inline-flex items-center rounded-full border border-[var(--border-strong)] px-3 py-1.5 text-sm text-[var(--text)] transition-colors hover:border-[var(--accent)] hover:text-[var(--accent)] ${className}`.trim()}
+    >
+      {theme === "dark" ? "Light mode" : "Dark mode"}
+    </button>
+  );
+}
diff --git a/content.ts b/content.ts
index fc03d650..f0117243 100644
--- a/content.ts
+++ b/content.ts
@@ -153,9 +153,10 @@ export const site = {
   // ---------------------------------------------------------------------------
   cookies: {
     // Short message shown in the banner. Keep it honest — this site does not
-    // currently use any tracking cookies, only one preference for consent.
+    // currently use any tracking cookies, only small preferences for consent
+    // and theme choice.
     message:
-      "Heads up — this site stores one tiny browser preference to remember your cookie choice. We don’t run analytics, advertising, or third-party tracking.",
+      "Heads up — this site stores small browser preferences to remember your cookie choice and theme selection. We don’t run analytics, advertising, or third-party tracking.",
 
     // The two buttons. Labels are small jokes for network folk; subtitles
     // and aria-labels make them clear to everyone else.