diff --git a/.env.example b/.env.example
index f5799af..83b7420 100644
--- a/.env.example
+++ b/.env.example
@@ -12,6 +12,11 @@ SECRET=
 NODE_ENV=production
 PORT=3000
 
+# Cookie Security (Optional)
+# Set to 'false' if accessing over HTTP (e.g., local LAN without HTTPS)
+# When unset, auto-detects HTTPS via X-Forwarded-Proto header
+# COOKIE_SECURE=false
+
 # Timezone for logs (Optional)
 TZ=America/New_York
 
diff --git a/README.md b/README.md
index 09995a3..de86c5d 100644
--- a/README.md
+++ b/README.md
@@ -102,6 +102,11 @@ PGID=1000
 # Optional - JWT Secret (auto-generated if not provided)
 # Generate with: openssl rand -base64 32
 SECRET=
+
+# Optional - Cookie Security
+# Set to 'false' for HTTP access (e.g., local LAN without HTTPS)
+# When unset, auto-detects HTTPS via X-Forwarded-Proto header
+COOKIE_SECURE=false
 ```
 
 ### User Permissions (PUID/PGID)
diff --git a/app/api/auth/login/route.ts b/app/api/auth/login/route.ts
index 22c5289..f4b54c4 100644
--- a/app/api/auth/login/route.ts
+++ b/app/api/auth/login/route.ts
@@ -1,5 +1,5 @@
 import { NextRequest, NextResponse } from 'next/server';
-import { generateAccessToken, generateRefreshToken, validateAdminCredentials } from '@/lib/auth/utils';
+import { generateAccessToken, generateRefreshToken, validateAdminCredentials, isSecureCookie } from '@/lib/auth/utils';
 
 export async function POST(request: NextRequest) {
   try {
@@ -36,7 +36,7 @@ export async function POST(request: NextRequest) {
     // Set cookies
     const cookieOptions = {
       httpOnly: true,
-      secure: process.env.NODE_ENV === 'production',
+      secure: isSecureCookie(request),
       sameSite: 'lax' as const,
       path: '/',
     };
diff --git a/app/api/auth/refresh/route.ts b/app/api/auth/refresh/route.ts
index 677053c..537461f 100644
--- a/app/api/auth/refresh/route.ts
+++ b/app/api/auth/refresh/route.ts
@@ -1,5 +1,5 @@
 import { NextRequest, NextResponse } from 'next/server';
-import { generateAccessToken, generateRefreshToken, verifyRefreshToken } from '@/lib/auth/utils';
+import { generateAccessToken, generateRefreshToken, verifyRefreshToken, isSecureCookie } from '@/lib/auth/utils';
 
 export async function POST(request: NextRequest) {
   try {
@@ -49,7 +49,7 @@ export async function POST(request: NextRequest) {
     // Set new cookies
     const cookieOptions = {
       httpOnly: true,
-      secure: process.env.NODE_ENV === 'production',
+      secure: isSecureCookie(request),
       sameSite: 'lax' as const,
       path: '/',
     };
diff --git a/app/api/lock/route.ts b/app/api/lock/route.ts
index 3d653bb..7b592cd 100644
--- a/app/api/lock/route.ts
+++ b/app/api/lock/route.ts
@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from 'next/server';
 import { eq } from 'drizzle-orm';
 import { db, settings } from '@/lib/db';
 import crypto from 'crypto';
+import { isSecureCookie } from '@/lib/auth/utils';
 
 // POST /api/lock - Verify password
 export async function POST(request: NextRequest) {
@@ -41,12 +42,11 @@ export async function POST(request: NextRequest) {
         message: 'Password verified',
       });
 
-      // Set an unlock cookie that expires in 24 hours
       response.cookies.set('site_unlocked', 'true', {
         httpOnly: true,
-        secure: process.env.NODE_ENV === 'production',
+        secure: isSecureCookie(request),
         sameSite: 'lax',
-        maxAge: 60 * 60 * 24, // 24 hours
+        maxAge: 60 * 60 * 24,
         path: '/',
       });
 
diff --git a/lib/auth/utils.ts b/lib/auth/utils.ts
index 83f1781..f69920e 100644
--- a/lib/auth/utils.ts
+++ b/lib/auth/utils.ts
@@ -128,3 +128,16 @@ export function validateAdminCredentials(username: string, password: string): bo
 
   return username === adminUsername && password === adminPassword;
 }
+
+export function isSecureCookie(request: { headers: { get(name: string): string | null }; url: string }): boolean {
+  if (process.env.COOKIE_SECURE !== undefined) {
+    return process.env.COOKIE_SECURE === 'true';
+  }
+  if (process.env.NODE_ENV === 'production') {
+    return (
+      request.headers.get('x-forwarded-proto') === 'https' ||
+      request.url.startsWith('https://')
+    );
+  }
+  return false;
+}