diff --git a/apps/as/app/layout.tsx b/apps/as/app/layout.tsx
index d152e0da3..f08c67ca7 100644
--- a/apps/as/app/layout.tsx
+++ b/apps/as/app/layout.tsx
@@ -1,6 +1,9 @@
 import type { Metadata } from "next";
+import { cookies } from "next/headers";
 import { Noto_Sans_KR } from "next/font/google";
 import { Providers } from "./providers";
+import { setCookie } from "@/shared/lib";
+import { SITE_ID } from "@/shared/config";
 import "./globals.css";
 
 const notoSansKR = Noto_Sans_KR({
@@ -19,9 +22,13 @@ interface RootLayoutProps {
   children: React.ReactNode;
 }
 
-export default function RootLayout({ children }: RootLayoutProps) {
+setCookie("site-id-key", SITE_ID);
+
+export default async function RootLayout({ children }: RootLayoutProps) {
+  const theme = (await cookies()).get("site-theme-key");
+
   return (
-    <html lang="ko" className={notoSansKR.variable}>
+    <html lang="ko" className={notoSansKR.variable} data-theme={theme?.value}>
       <body className={`${notoSansKR.className} antialiased`}>
         <Providers>{children}</Providers>
       </body>
diff --git a/apps/as/package.json b/apps/as/package.json
index fb27f8af7..3806f73ee 100644
--- a/apps/as/package.json
+++ b/apps/as/package.json
@@ -19,11 +19,13 @@
     "@tanstack/react-table": "^8.21.2",
     "axios": "^1.8.1",
     "dayjs": "^1.11.13",
+    "js-cookie": "^3.0.5",
     "next": "15.3.8",
     "react-hook-form": "^7.54.2",
     "zod": "^3.24.2"
   },
   "devDependencies": {
+    "@types/js-cookie": "^3.0.6",
     "eslint": "^9.0.0",
     "eslint-config-next": "15.4.0",
     "postcss": "^8.4.49",
diff --git a/apps/as/shared/lib/cookie.ts b/apps/as/shared/lib/cookie.ts
new file mode 100644
index 000000000..6557cb81d
--- /dev/null
+++ b/apps/as/shared/lib/cookie.ts
@@ -0,0 +1,22 @@
+import Cookies from "js-cookie";
+
+export function getCookie(name: string): string | undefined {
+  if (typeof window === "undefined") {
+    return undefined;
+  }
+  return Cookies.get(name);
+}
+
+export function setCookie(name: string, value: string, options?: Cookies.CookieAttributes): void {
+  if (typeof window === "undefined") {
+    return;
+  }
+  Cookies.set(name, value, options);
+}
+
+export function removeCookie(name: string, options?: Cookies.CookieAttributes): void {
+  if (typeof window === "undefined") {
+    return;
+  }
+  Cookies.remove(name, options);
+}
diff --git a/apps/as/shared/lib/index.ts b/apps/as/shared/lib/index.ts
index 51e9c2c5d..26a6d4551 100644
--- a/apps/as/shared/lib/index.ts
+++ b/apps/as/shared/lib/index.ts
@@ -1,2 +1,3 @@
 export { queryClient } from "./query-client";
 export { dayjs } from "./dayjs";
+export { getCookie, setCookie, removeCookie } from "./cookie";
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index f78691690..569437868 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -80,6 +80,9 @@ importers:
       dayjs:
         specifier: ^1.11.13
         version: 1.11.19
+      js-cookie:
+        specifier: ^3.0.5
+        version: 3.0.5
       next:
         specifier: 15.3.8
         version: 15.3.8(react-dom@19.2.3(react@19.2.3))(react@19.2.3)
@@ -90,6 +93,9 @@ importers:
         specifier: ^3.24.2
         version: 3.25.76
     devDependencies:
+      '@types/js-cookie':
+        specifier: ^3.0.6
+        version: 3.0.6
       eslint:
         specifier: ^9.0.0
         version: 9.39.2(jiti@1.21.7)