diff --git a/background.js b/background.js
new file mode 100644
index 0000000..d86bfad
--- /dev/null
+++ b/background.js
@@ -0,0 +1,47 @@
+/* eslint-disable no-undef */
+// https://stackoverflow.com/a/45985333
+function getBrowser() {
+	if (typeof chrome !== "undefined") {
+		if (typeof browser !== "undefined") {
+			return "Firefox";
+		} else {
+			return "Chrome";
+		}
+	} else {
+		return "Edge";
+	}
+}
+
+chrome.webRequest.onBeforeRequest.addListener(
+	function (details) {
+		if (getBrowser() == "Chrome") {
+			return { redirectUrl: chrome.runtime.getURL("cadmium-playercore-shim.js") };
+		}
+		
+		/* Work around funky CORS behaviour on Firefox */
+		else if (getBrowser() == "Firefox") {
+			let filter = browser.webRequest.filterResponseData(details.requestId);
+			let encoder = new TextEncoder();
+			filter.onstop = () => {
+				fetch(browser.runtime.getURL("cadmium-playercore-shim.js")).
+					then(response => response.text()).
+					then(text => {
+						filter.write(encoder.encode(text));
+						filter.close();
+					});
+			};
+			return {};
+		}
+		
+		else {
+			console.error("Unsupported web browser.");
+			return {};
+		}
+	}, {
+		urls: [
+			"*://assets.nflxext.com/*/ffe/player/html/*",
+			"*://www.assets.nflxext.com/*/ffe/player/html/*"
+		],
+		types: ["script"]
+	}, ["blocking"]
+);
diff --git a/cadmium-playercore-shim.js b/cadmium-playercore-shim.js
index 2cfef06..a6e9fcc 100644
--- a/cadmium-playercore-shim.js
+++ b/cadmium-playercore-shim.js
@@ -41,7 +41,7 @@ function do_patch(desc, needle, replacement) {
 the response before the body of this script finishes executing */
 var request = new XMLHttpRequest();
 var cadmium_url = document.getElementById("player-core-js").src;
-request.open("GET", cadmium_url, false); // synchronous
+request.open("GET", cadmium_url + "?no_filter", false); // synchronous
 request.send();
 
 var cadmium_src = request.responseText;
diff --git a/manifest.json b/manifest.json
index ff4ef89..183255f 100644
--- a/manifest.json
+++ b/manifest.json
@@ -1,10 +1,10 @@
 {
-	"manifest_version": 3,
+	"manifest_version": 2,
 	"name": "Netflix International",
 	"description": "Displays all available Netflix audio and subtitle tracks.",
-	"version": "2.0.23",
+	"version": "2.0.21",
 	"author": "shirt",
-	"action": {
+	"browser_action": {
 	  "default_icon": "img/icon128.png",
 	  "default_popup": "pages/options.html"
 	},
@@ -19,6 +19,8 @@
 	},
 	"content_scripts": [{
 	  "matches": [
+		"*://assets.nflxext.com/*/ffe/player/html/*",
+		"*://www.assets.nflxext.com/*/ffe/player/html/*",
 		"*://netflix.com/*",
 		"*://www.netflix.com/*"
 	  ],
@@ -27,35 +29,24 @@
 	  "js": ["content_script.js"],
 	  "run_at": "document_start"
 	}],
+	"background": {
+	  "scripts": ["background.js"]
+	},
 	"options_ui": {
 	  "page": "pages/options.html",
 	  "open_in_tab": true
 	},
-	"web_accessible_resources": [{
-		"resources": [
-			"cadmium-playercore-shim.js",
-			"netflix_max_bitrate.js",
-			"netflix.css"
-		],
-		"matches": [
-			"*://assets.nflxext.com/*",
-			"*://netflix.com/*",
-			"*://www.netflix.com/*"
-		]
-	}],
-	"declarative_net_request" : {
-		"rule_resources" : [{
-			"id": "1",
-			"enabled": true,
-			"path": "rules.json"
-		}]
-	},
+	"web_accessible_resources": [
+	  "cadmium-playercore-shim.js",
+	  "netflix_max_bitrate.js",
+	  "netflix.css"
+	],
 	"permissions": [
 	  "storage",
-	  "declarativeNetRequestWithHostAccess"
-	],
-	"host_permissions": [
-	  "*://assets.nflxext.com/*",
+	  "webRequest",
+	  "webRequestBlocking",
+	  "*://assets.nflxext.com/*/ffe/player/html/*",
+	  "*://www.assets.nflxext.com/*/ffe/player/html/*",
 	  "*://netflix.com/*",
 	  "*://www.netflix.com/*"
 	]
diff --git a/rules.json b/rules.json
deleted file mode 100644
index a948a65..0000000
--- a/rules.json
+++ /dev/null
@@ -1,26 +0,0 @@
-[
-    {
-        "id": 1,
-        "priority": 1,
-        "action": {
-            "type": "redirect",
-            "redirect": { "extensionPath": "/cadmium-playercore-shim.js" }
-        },
-        "condition": {
-            "urlFilter": "*://assets.nflxext.com/*/ffe/player/html/*",
-            "resourceTypes": ["script"]
-        }
-    },
-    {
-        "id": 2,
-        "priority": 1,
-        "action": {
-            "type": "redirect",
-            "redirect": { "extensionPath": "/cadmium-playercore-shim.js" }
-        },
-        "condition": {
-            "urlFilter": "*://assets.nflxext.com/player/html/ffe/*",
-            "resourceTypes": ["script"]
-        }
-    }
-]