diff --git a/docs/script.js b/docs/script.js
index 70c43c4..99d5def 100644
--- a/docs/script.js
+++ b/docs/script.js
@@ -3,6 +3,25 @@
 (function () {
   'use strict';
 
+  /* --- macOS Notice --- */
+  // iPadOS reports platform 'MacIntel' too, so require a non-touch device.
+  var isMac = /Mac/.test(navigator.platform) && navigator.maxTouchPoints <= 1;
+  if (isMac && sessionStorage.getItem('mac-notice-dismissed') !== '1') {
+    var notice = document.createElement('div');
+    notice.className = 'mac-notice';
+    notice.innerHTML =
+      '<p><strong>Looks like you\'re on a Mac.</strong>' +
+      'EternalMonitor is Windows-only for now. The good news: macOS already does this ' +
+      'for free with <a href="https://support.apple.com/en-us/102386" target="_blank" rel="noopener">Sidecar</a>, ' +
+      'which turns your iPad into a second display natively and works well.</p>' +
+      '<button type="button" class="mac-notice-close" aria-label="Dismiss">&times;</button>';
+    notice.querySelector('.mac-notice-close').addEventListener('click', function () {
+      sessionStorage.setItem('mac-notice-dismissed', '1');
+      notice.remove();
+    });
+    document.body.appendChild(notice);
+  }
+
   /* --- Scroll Reveal (IntersectionObserver) --- */
   var reveals = document.querySelectorAll('.reveal');
   if (reveals.length && 'IntersectionObserver' in window) {
diff --git a/docs/style.css b/docs/style.css
index 4436d96..842a71e 100644
--- a/docs/style.css
+++ b/docs/style.css
@@ -986,3 +986,58 @@ section {
     padding: 120px 0;
   }
 }
+
+/* --- macOS Notice Bar --- */
+.mac-notice {
+  position: fixed;
+  left: 16px;
+  right: 16px;
+  bottom: 16px;
+  z-index: 200;
+  display: flex;
+  align-items: flex-start;
+  gap: 16px;
+  max-width: 720px;
+  margin: 0 auto;
+  padding: 24px 28px;
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: var(--radius-md);
+  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.5);
+}
+
+.mac-notice p {
+  margin: 0;
+  font-size: 1rem;
+  line-height: 1.6;
+  color: var(--muted);
+}
+
+.mac-notice strong {
+  display: block;
+  margin-bottom: 6px;
+  color: var(--text);
+  font-family: var(--font-display);
+  font-weight: 700;
+  font-size: 1.15rem;
+}
+
+.mac-notice a {
+  color: var(--accent);
+}
+
+.mac-notice-close {
+  flex-shrink: 0;
+  margin-left: auto;
+  padding: 4px 8px;
+  background: none;
+  border: none;
+  color: var(--muted);
+  font-size: 1.1rem;
+  line-height: 1;
+  cursor: pointer;
+}
+
+.mac-notice-close:hover {
+  color: var(--text);
+}