diff --git a/.gitignore b/.gitignore
index f5a083b..497cd73 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 config.json
+.demo
 data/
 .DS_Store
diff --git a/setup.php b/setup.php
index 1f5a4fa..ec21324 100644
--- a/setup.php
+++ b/setup.php
@@ -1,5 +1,6 @@
 <?php
 $config_path = __DIR__ . '/config.json';
+$demo_mode = file_exists(__DIR__ . '/.demo');
 
 // Automatically migrate the legacy config format.
 if (file_exists($config_path)) {
@@ -41,7 +42,9 @@ $error   = '';
 $new_key = '';
 
 if (!$is_first_setup) {
-    if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['admin_key_input'])) {
+    if ($demo_mode) {
+        $mode = 'setup';
+    } elseif ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['admin_key_input'])) {
         if (trim($_POST['admin_key_input']) === $admin_key) {
             $mode = 'setup';
         } else {
@@ -61,6 +64,9 @@ if (!$is_first_setup) {
 }
 
 if ($mode === 'setup' && $_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['group_name'])) {
+    if ($demo_mode) {
+        $error = 'Demo mode is enabled. Configuration is read-only on this instance.';
+    } else {
     $group_name         = trim($_POST['group_name'] ?? '');
     $allow_personal_epg = isset($_POST['allow_personal_epg']);
 
@@ -107,6 +113,7 @@ if ($mode === 'setup' && $_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['
             }
         }
     }
+    }
 }
 
 $prefill_group   = $_POST['group_name'] ?? $existing['group_name']     ?? '';
@@ -182,12 +189,19 @@ $submitted_key   = trim($_POST['admin_key_input'] ?? $_POST['admin_key_hidden']
   .lock-form input{flex:1;}
   .setup-note{margin-top:28px;padding-top:20px;border-top:1px solid var(--border);font-size:11px;color:var(--text-dim);line-height:1.6;}
   .setup-note code{font-family:'Share Tech Mono',monospace;background:var(--surface2);padding:1px 5px;border:1px solid var(--border);color:var(--accent2);font-size:11px;}
+  .demo-banner{padding:12px 14px;font-size:13px;margin-bottom:24px;line-height:1.5;border-left:3px solid var(--accent2);background:rgba(74,158,255,.08);color:var(--text-bright);}
+  .readonly-wrap{opacity:.82;}
+  .readonly-hint{margin-top:12px;font-size:12px;color:var(--text-dim);line-height:1.5;}
 </style>
 </head>
 <body>
 <div class="setup-card">
   <div class="setup-logo">Grid<span>/</span>TV</div>
 
+  <?php if ($demo_mode): ?>
+    <div class="demo-banner">Demo mode is enabled on this instance. Visitors can view the current configuration, but saving changes is disabled.</div>
+  <?php endif; ?>
+
   <?php if ($mode === 'lock'): ?>
     <div class="setup-subtitle">Enter your admin key to access the configuration.</div>
     <?php if ($error): ?><div class="alert alert-error"><?= htmlspecialchars($error) ?></div><?php endif; ?>
@@ -219,7 +233,7 @@ $submitted_key   = trim($_POST['admin_key_input'] ?? $_POST['admin_key_hidden']
 
   <?php else: ?>
     <div class="setup-subtitle">
-      <?= $is_first_setup ? 'Welcome to GridTV. Fill in the fields below to get started.' : 'Edit your GridTV configuration.' ?>
+      <?= $is_first_setup ? 'Welcome to GridTV. Fill in the fields below to get started.' : ($demo_mode ? 'View the current GridTV configuration.' : 'Edit your GridTV configuration.') ?>
     </div>
     <?php if ($error): ?><div class="alert alert-error"><?= htmlspecialchars($error) ?></div><?php endif; ?>
 
@@ -227,6 +241,7 @@ $submitted_key   = trim($_POST['admin_key_input'] ?? $_POST['admin_key_hidden']
       <?php if (!$is_first_setup): ?>
         <input type="hidden" name="admin_key_hidden" value="<?= htmlspecialchars($submitted_key ?: $admin_key) ?>">
       <?php endif; ?>
+      <?php if ($demo_mode): ?><div class="readonly-wrap"><fieldset disabled style="border:none;padding:0;margin:0"><?php endif; ?>
 
       <div class="form-group">
         <label>TV Group Name <span class="required">*</span></label>
@@ -274,7 +289,10 @@ $submitted_key   = trim($_POST['admin_key_input'] ?? $_POST['admin_key_hidden']
         </label>
       </div>
 
+      <?php if (!$demo_mode): ?>
       <button type="submit" class="btn-submit">Save configuration</button>
+      <?php endif; ?>
+      <?php if ($demo_mode): ?></fieldset></div><div class="readonly-hint">Saving is disabled in demo mode. Remove the <code>.demo</code> file on the server to restore normal editing.</div><?php endif; ?>
     </form>
 
   <?php endif; ?>
diff --git a/src/lib/admin.php b/src/lib/admin.php
index 4c14170..c969a86 100644
--- a/src/lib/admin.php
+++ b/src/lib/admin.php
@@ -3,6 +3,10 @@
 require_once __DIR__ . '/common.php';
 
 function gridtv_require_admin(array $config, string $page_title = 'Admin'): array {
+    if (gridtv_is_demo_mode()) {
+        return ['unlocked' => true, 'error' => '', 'demo' => true];
+    }
+
     if (session_status() !== PHP_SESSION_ACTIVE) {
         session_start();
     }
@@ -12,7 +16,7 @@ function gridtv_require_admin(array $config, string $page_title = 'Admin'): arra
     $error = '';
 
     if ($admin_key !== '' && hash_equals($admin_key, (string) $session_key)) {
-        return ['unlocked' => true, 'error' => ''];
+        return ['unlocked' => true, 'error' => '', 'demo' => false];
     }
 
     if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['admin_key_input'])) {
diff --git a/src/lib/common.php b/src/lib/common.php
index 00db619..388d72b 100644
--- a/src/lib/common.php
+++ b/src/lib/common.php
@@ -4,6 +4,14 @@ function gridtv_config_path(): string {
     return dirname(__DIR__, 2) . '/config.json';
 }
 
+function gridtv_demo_path(): string {
+    return dirname(__DIR__, 2) . '/.demo';
+}
+
+function gridtv_is_demo_mode(): bool {
+    return file_exists(gridtv_demo_path());
+}
+
 function gridtv_load_config(): array {
     $config_path = gridtv_config_path();
     if (!file_exists($config_path)) {
