diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8dea263
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/dist/
+.amo-upload-uuid
\ No newline at end of file
diff --git a/background.js b/background.js
index b2a85d4..e1c7b56 100644
--- a/background.js
+++ b/background.js
@@ -1,18 +1,73 @@
 "use strict";
 
-const WINDOWS_CHROME_UA =
-  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) " +
-  "AppleWebKit/537.36 (KHTML, like Gecko) " +
-  "Chrome/140.0.0.0 Safari/537.36";
+const CHROME_VERSION = "140.0.0.0";
+const TARGET_HOSTS = [
+  "netflix.com",
+  "assets.nflxext.com"
+];
 
-browser.webRequest.onBeforeSendHeaders.addListener(
+function getOperatingSystem() {
+  const ua = globalThis.navigator?.userAgent || "";
+  const platform = globalThis.navigator?.platform || "";
+  const userAgentDataPlatform = globalThis.navigator?.userAgentData?.platform || "";
+
+  if (/Windows/i.test(ua) || /Win/i.test(platform) || /win/i.test(userAgentDataPlatform)) {
+    return "win";
+  }
+
+  if (/Mac/i.test(ua) || /Mac/i.test(platform) || /mac/i.test(userAgentDataPlatform)) {
+    return "mac";
+  }
+
+  if (/Linux/i.test(ua) || /Linux/i.test(platform) || /linux/i.test(userAgentDataPlatform)) {
+    return "linux";
+  }
+
+  return "linux";
+}
+
+function getChromeLikeUserAgent() {
+  const os = getOperatingSystem();
+
+  switch (os) {
+    case "mac":
+      return `Mozilla/5.0 (Macintosh; Intel Mac OS X 14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/${CHROME_VERSION} Safari/537.36`;
+    case "win":
+      return `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/${CHROME_VERSION} Safari/537.36`;
+    case "linux":
+    default:
+      return `Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/${CHROME_VERSION} Safari/537.36`;
+  }
+}
+
+function isTargetHost(url) {
+  try {
+    const hostname = new URL(url).hostname.toLowerCase();
+
+    return hostname === "netflix.com" ||
+      hostname.endsWith(".netflix.com") ||
+      hostname === "assets.nflxext.com" ||
+      hostname.endsWith(".nflxext.com");
+  } catch {
+    return false;
+  }
+}
+
+const browserApi = globalThis.browser || globalThis.chrome;
+
+browserApi.webRequest.onBeforeSendHeaders.addListener(
   (details) => {
+    if (!isTargetHost(details.url)) {
+      return {};
+    }
+
     const requestHeaders = details.requestHeaders ?? [];
+    const userAgentValue = getChromeLikeUserAgent();
     let foundUserAgent = false;
 
     for (const header of requestHeaders) {
       if (header.name.toLowerCase() === "user-agent") {
-        header.value = WINDOWS_CHROME_UA;
+        header.value = userAgentValue;
         foundUserAgent = true;
         break;
       }
@@ -21,7 +76,7 @@ browser.webRequest.onBeforeSendHeaders.addListener(
     if (!foundUserAgent) {
       requestHeaders.push({
         name: "User-Agent",
-        value: WINDOWS_CHROME_UA
+        value: userAgentValue
       });
     }
 
@@ -30,7 +85,9 @@ browser.webRequest.onBeforeSendHeaders.addListener(
   {
     urls: [
       "*://netflix.com/*",
-      "*://*.netflix.com/*"
+      "*://*.netflix.com/*",
+      "*://assets.nflxext.com/*",
+      "*://*.nflxext.com/*"
     ]
   },
   [
diff --git a/manifest.json b/manifest.json
index 033612b..2aa77c5 100644
--- a/manifest.json
+++ b/manifest.json
@@ -1,8 +1,8 @@
 {
   "manifest_version": 3,
-  "name": "thisiswindowschromiumnetflix",
-  "version": "1.0.0",
-  "description": "Netflix에서 User-Agent를 Windows Chrome으로 고정합니다.",
+  "name": "thisischromiumnetflix",
+  "version": "2026.7.27.1",
+  "description": "Netflix 관련 요청의 User-Agent를 운영체제에 맞춰 조정합니다.",
 
   "permissions": [
     "webRequest",
@@ -23,7 +23,7 @@
   "browser_specific_settings": {
     "gecko": {
       "id": "thisiswindowschromiumnetflix@imnya.ng",
-      "strict_min_version": "109.0",
+      "strict_min_version": "142.0",
       "data_collection_permissions": {
         "required": [
           "none"
@@ -31,4 +31,4 @@
       }
     }
   }
-}
\ No newline at end of file
+}