ScratchAddons · mxmou · Dec 4, 2025 · Nov 19, 2025 · Nov 19, 2025 · Nov 28, 2025
@@ -1,4 +1,5 @@
 import Listenable from "./Listenable.js";
+import { isFirefox } from "../../libraries/common/cs/detect-browser.js";
 
 /**
  * Represents information about the addon.
@@ -13,8 +14,7 @@ export default class Self extends Listenable {
     this._addonId = info.id; // In order to receive fireEvent messages from background
     this.id = info.id;
     this._addonObj = addonObj;
-    // catches both Chrome and Chromium
-    this.browser = /Chrom/.test(navigator.userAgent) ? "chrome" : "firefox";
+    this.browser = isFirefox() ? "firefox" : "chrome";
     this.disabled = false;
     this.addEventListener("disabled", () => (this.disabled = true));
     this.addEventListener("reenabled", () => (this.disabled = false));

diff --git a/addons/gamepad/gamepadlib.js b/addons/gamepad/gamepadlib.js
@@ -1,3 +1,5 @@
+import { isFirefox } from "../../libraries/common/cs/detect-browser.js";
+
 let console = window.console;
 
 /*
@@ -652,7 +654,7 @@ GamepadLib.browserHasBrokenGamepadAPI = () => {
   // Firefox on Linux before version 123 has a broken gamepad API that results in strange and unusable mappings
   // https://bugzilla.mozilla.org/show_bug.cgi?id=1680982
   // https://bugzilla.mozilla.org/show_bug.cgi?id=1643835
-  if (navigator.userAgent.includes("Firefox") && navigator.userAgent.includes("Linux")) {
+  if (isFirefox() && navigator.userAgent.includes("Linux")) {
     const agentMatch = navigator.userAgent.match(/Firefox\/(\d+)/);
     // If we couldn't find the version number, we'll assume that this is some distant future version of
     // Firefox that we just can't comprehend with the technology of today. Surely gamepad will work well
@@ -662,7 +664,7 @@ GamepadLib.browserHasBrokenGamepadAPI = () => {
   }
   // Firefox on macOS has other bugs that result in strange and unusable mappings
   // eg. https://bugzilla.mozilla.org/show_bug.cgi?id=1434408
-  if (navigator.userAgent.includes("Firefox") && navigator.userAgent.includes("Mac OS")) {
+  if (isFirefox() && navigator.userAgent.includes("Mac OS")) {
     return true;
   }
   return false;

@@ -1,4 +1,6 @@
-if (typeof browser === "object" && chrome.scripting) {
+import { isFirefox } from "../libraries/common/cs/detect-browser.js";
+
+if (isFirefox() && chrome.scripting) {
   const manifest = chrome.runtime.getManifest();
   const manifestScripts = manifest.content_scripts.filter((script) =>
     script.matches.includes("http://localhost:8601/*")

@@ -1,6 +1,7 @@
 import { startCache } from "./message-cache.js";
 import { openMessageCache } from "../libraries/common/message-cache.js";
 import { purgeDatabase } from "../addons/scratch-notifier/notifier.js";
+import { isFirefox } from "../libraries/common/cs/detect-browser.js";
 
 async function getDefaultStoreId() {
   const CHROME_DEFAULT = "0";
@@ -168,8 +169,7 @@ function notify(cookie) {
   if (cookie.name === "scratchlanguage") return;
   const storeId = cookie.storeId;
   const cond = {};
-  if (typeof browser === "object") {
-    // Firefox-exclusive.
+  if (isFirefox()) {
     cond.cookieStoreId = storeId;
   }
   // On Chrome this can cause unnecessary session re-fetch, but there should be

@@ -1,3 +1,5 @@
+import { isFirefox } from "../libraries/common/cs/detect-browser.js";
+
 const dataURLToArrayBuffer = function (dataURL) {
   const byteString = atob(dataURL.split(",")[1]);
   const arrayBuffer = new ArrayBuffer(byteString.length);
@@ -8,8 +10,7 @@ const dataURLToArrayBuffer = function (dataURL) {
   return arrayBuffer;
 };
 
-if (typeof browser !== "undefined") {
-  // Firefox
+if (isFirefox()) {
   browser.runtime.onMessage.addListener(function (request) {
     if (request.clipboardDataURL && browser && browser.clipboard && browser.clipboard.setImageData) {
       const arrayBuffer = dataURLToArrayBuffer(request.clipboardDataURL);

@@ -1,7 +1,8 @@
+import { isFirefox } from "../../libraries/common/cs/detect-browser.js";
+
 // REMINDER: update similar code at /webpages/settings/index.js
 const browserLevelPermissions = ["notifications"];
-if (typeof browser !== "undefined") {
-  // Firefox only
+if (isFirefox()) {
   if (typeof Clipboard.prototype.write !== "function") {
     // Firefox 109-126 only
     browserLevelPermissions.push("clipboardWrite");

@@ -0,0 +1,3 @@
+export function isFirefox() {
+  return typeof new Error().fileName !== "undefined";
+}
@@ -1,3 +1,5 @@
+import { isFirefox } from "./cs/detect-browser.js";
+
 let id = 0;
 
 export default function create(opts) {
@@ -7,7 +9,7 @@ export default function create(opts) {
   if (scratchAddons.muted) return Promise.resolve(null);
   const notifId = `${opts.base}__${Date.now()}_${id++}`;
   let newOpts;
-  if (!/Chrom/.test(navigator.userAgent)) {
+  if (isFirefox()) {
     newOpts = JSON.parse(JSON.stringify(opts));
     // On Firefox, remove notification properties that throw.
     delete newOpts.buttons;

diff --git a/webpages/settings/index.js b/webpages/settings/index.js
@@ -9,6 +9,7 @@ import exampleManifest from "./data/example-manifest.js";
 import fuseOptions from "./data/fuse-options.js";
 import globalTheme from "../../libraries/common/global-theme.js";
 import { deserializeSettings, serializeSettings } from "./settings-utils.js";
+import { isFirefox } from "../../libraries/common/cs/detect-browser.js";
 
 let isIframe = false;
 if (window.parent !== window) {
@@ -64,8 +65,7 @@ let fuse;
 
   // REMINDER: update similar code at /background/imports/util.js
   const browserLevelPermissions = ["notifications"];
-  if (typeof browser !== "undefined") {
-    // Firefox only
+  if (isFirefox()) {
     if (typeof Clipboard.prototype.write !== "function") {
       // Firefox 109-126 only
       browserLevelPermissions.push("clipboardWrite");
@@ -385,8 +385,7 @@ let fuse;
       // Autofocus search bar in iframe mode for both browsers
       // autofocus attribute only works in Chrome for us, so
       // we also manually focus on Firefox, even in fullscreen
-      if (isIframe || typeof browser !== "undefined")
-        setTimeout(() => document.getElementById("searchBox")?.focus(), 0);
+      if (isIframe || isFirefox()) setTimeout(() => document.getElementById("searchBox")?.focus(), 0);
 
       const exampleAddonListItem = {
         // Need to specify all used properties for reactivity!