diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ad0c893..b597bbb 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -23,8 +23,10 @@ jobs:
         run: bun install --frozen-lockfile
       - name: Run Typecheck
         run: bun run typecheck
-      - name: Build Extension
+      - name: Build Extension (Chrome MV3)
         run: bun run build
+      - name: Build Extension (Firefox MV2)
+        run: bun run build:firefox
 
   # release job, runs on main only after successful build
   release:
diff --git a/README.md b/README.md
index c7f0473..5e5d218 100644
--- a/README.md
+++ b/README.md
@@ -44,20 +44,34 @@ npm run build
 npm run zip
 ```
 
-Firefox builds are also supported:
+To manually load the production build as an unpacked extension in Chrome:
+
+1. Run `npm run build`.
+2. Open `chrome://extensions/`.
+3. Enable Developer Mode (top right).
+4. Click "Load Unpacked" and select the `.output/chrome-mv3/` folder.
+
+### Firefox development
+
+Firefox builds (MV2) are also supported. WXT normalizes the MV3 manifest into
+the MV2 shape automatically; the `chrome.scripting.*` API used by the background
+worker is supported in Firefox 102 and later.
 
 ```bash
+# dev server with HMR, launches Firefox with the extension auto-loaded
 npm run dev:firefox
+
+# production build (writes to .output/firefox-mv2/)
 npm run build:firefox
+
+# zip for AMO submission (writes to .output/<name>-<ver>-firefox.zip)
 npm run zip:firefox
 ```
 
-To manually load the production build as an unpacked extension in Chrome:
-
-1. Run `npm run build`.
-2. Open `chrome://extensions/`.
-3. Enable Developer Mode (top right).
-4. Click "Load Unpacked" and select the `.output/chrome-mv3/` folder.
+To customise the browser binary that `npm run dev` / `npm run dev:firefox`
+launches (e.g. point at Firefox Developer Edition), copy
+`web-ext.config.example.ts` to `web-ext.config.ts` and edit the paths. The
+`web-ext.config.ts` file is gitignored — keep it local to your machine.
 
 ## License
 
diff --git a/web-ext.config.example.ts b/web-ext.config.example.ts
new file mode 100644
index 0000000..d521568
--- /dev/null
+++ b/web-ext.config.example.ts
@@ -0,0 +1,13 @@
+import { defineWebExtConfig } from "wxt"
+
+// Copy this file to `web-ext.config.ts` (gitignored) and adjust paths for your
+// machine. WXT uses it to launch the browser during `wxt` / `wxt -b firefox`.
+//
+// See https://wxt.dev/guide/essentials/config/browser-startup.html
+export default defineWebExtConfig({
+    binaries: {
+        chrome: "C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe",
+        firefox: "firefoxdeveloperedition",
+    },
+    startUrls: ["https://schoolbox.education/"],
+})
diff --git a/wxt.config.ts b/wxt.config.ts
index 31a6a47..9c737e9 100644
--- a/wxt.config.ts
+++ b/wxt.config.ts
@@ -3,6 +3,9 @@ import { defineConfig } from "wxt"
 // See https://wxt.dev/api/config.html
 export default defineConfig({
     srcDir: "src",
+    // Firefox MV2 build: WXT normalizes host_permissions, web_accessible_resources,
+    // and action -> browser_action automatically. The `scripting` permission and
+    // `chrome.scripting.*` API are supported in Firefox MV2 (Firefox 102+).
     manifest: {
         name: "UltraBox",
         description: "A Chrome extension for SchoolBox.",
@@ -29,4 +32,10 @@ export default defineConfig({
             },
         ],
     },
+    // UltraBox is an existing extension (currently distributed for Chrome). The
+    // Firefox data-collection consent requirement only applies to brand-new
+    // listings on AMO; suppress the build-time warning until we list there.
+    suppressWarnings: {
+        firefoxDataCollection: true,
+    },
 })