OverviewHistoryStatsSecurity
npx skills add ...
Documentation
SKILL.md
npx skills add samber/cc-skills --skill crxjs
CRXJS Chrome extension development — true HMR for popup, options, content scripts, side panels, manifest-driven builds, dynamic content script imports (`?script`, `?script&module`), and `defineManifest` for type-safe manifests. Uses Vite as its build tool. Use when the user mentions CRXJS, crxjs, @crxjs/vite-plugin, 'extension with hot reload', 'HMR for chrome extension', or wants to set up a CRXJS-based Chrome extension project with any framework (React, Vue, Svelte, Solid, Vanilla). Also trigger when the user has an existing CRXJS project and wants to add features, fix HMR issues, or configure content scripts with CRXJS. For general Chrome extension architecture (messaging, CSP, storage, permissions) -> See `samber/cc-skills@chrome-extension` skill.
npx skills add samber/cc-skills --skill crxjs
CRXJS is a Chrome extension development tool that provides true HMR for popup, options, content scripts, and side panels. It reads your manifest to auto-generate the extension output, handles content script injection, and manages the service worker build. Under the hood it is a Vite plugin (@crxjs/vite-plugin).
@crxjs/vite-plugin (v2.x stable, latest v2.4.0 as of March 2026)npm create crxjs@latest (always use @latest)CRXJS is added as a Vite plugin. The setup varies slightly per framework.
Use @vitejs/plugin-react (not plugin-react-swc) for best HMR compatibility. If you must use SWC, cast the manifest:
Instead of a static JSON file, use CRXJS's defineManifest for dynamic values and full TypeScript autocompletion:
Import in vite.config.ts:
Add to a src/vite-env.d.ts or src/crxjs.d.ts:
This enables types for ?script and ?script&module imports.
| Context | HMR | How it works |
|---|---|---|
| Popup | Full HMR | WebSocket-based, state preserved |
| Options page | Full HMR | Same as popup |
| Side panel | Full HMR | Same as popup |
| Content script (manifest) | True HMR | CRXJS injects loader + HMR client |
| Content script (dynamic) | True HMR | Via ?script import |
| Service worker | Auto-reload | Changes trigger full extension reload |
| Main world scripts | No HMR | Skipped by CRXJS loader |
Content script HMR works because CRXJS generates a loader script that imports an HMR preamble, the HMR client, and your actual script — enabling real module-level HMR without full page reload. This is CRXJS's main differentiator.
For content scripts injected programmatically (not in manifest), CRXJS provides special import suffixes:
For main world injection (no HMR):
After loading once, subsequent npm run dev sessions reconnect automatically. No need to re-load the extension unless manifest.json changes.
The dist/ directory is ready to zip and upload to Chrome Web Store:
Disable Vite's module preload to avoid CWS rejection of inline scripts:
New Tailwind classes may not trigger CSS updates in content scripts. Workaround: restart dev server after adding new utility classes. Improved in v2.4.0 but not fully resolved. Ensure injectCss: true in config.
ws://localhost:undefined/)Cause: port mismatch between dev server and HMR config. Fix: explicitly set both to the same value:
If you see this, your manifest is being interpreted as MV2. Fix: ensure "manifest_version": 3 is set.
Chrome requires the user to enable "Allow access to file URLs" in the extension settings at chrome://extensions. CRXJS cannot change this.
CRXJS's HMR relies on injecting a content script that connects to the dev server's WebSocket. Chrome security updates occasionally break this. Fix: update to the latest CRXJS version, which tracks Chrome changes.
| Feature | CRXJS | WXT | Plasmo |
|---|---|---|---|
| Content script HMR | True HMR | File-based reload | Partial |
| Framework support | Any Vite framework | Any | React-focused |
| Abstraction level | Thin (Vite plugin) | Full framework | Full framework |
| Messaging helpers | None (use chrome.* directly) | Built-in | Built-in |
| Storage wrappers | None | Built-in | Built-in |
| Cross-browser | Chrome + Firefox | Chrome + Firefox + Safari | Chrome + Firefox |
| File-based routing | No | Yes | Yes |
| Learning curve | Low (know Vite, know CRXJS) | Medium | Medium |
Choose CRXJS when: you want minimal abstraction over raw Chrome APIs and value content script HMR above all. CRXJS stays out of the way — no magic routing, no wrapper APIs, just your code with HMR.
Choose WXT when: you want conventions, built-in utilities, and cross-browser support.
Choose Plasmo when: you're React-focused and want the highest-level abstraction.
CRXJS resolves HTML files referenced in the manifest automatically. Your popup.html can use standard <script type="module" src="./main.tsx"> and it works.
If you encounter a bug or unexpected behavior in CRXJS, open an issue at github.com/crxjs/chrome-extension-tools/issues.
import { ManifestV3Export } from "@crxjs/vite-plugin";
const manifest = manifestJson as ManifestV3Export;import vue from "@vitejs/plugin-vue";
import { crx } from "@crxjs/vite-plugin";
import manifest from "./manifest.json";
export default defineConfig({
plugins: [vue(), crx({ manifest })],
});import { svelte } from "@sveltejs/vite-plugin-svelte";
import { crx } from "@crxjs/vite-plugin";
import manifest from "./manifest.json";
export default defineConfig({
plugins: [svelte(), crx({ manifest })],
});import { crx } from "@crxjs/vite-plugin";
import manifest from "./manifest.json";
export default defineConfig({
plugins: [crx({ manifest })],
});// manifest.ts
import { defineManifest } from "@crxjs/vite-plugin";
import pkg from "./package.json";
export default defineManifest((config) => ({
manifest_version: 3,
name: config.command === "serve" ? `[DEV] ${pkg.name}` : pkg.name,
version: pkg.version,
description: pkg.description,
permissions: ["storage", "activeTab", "scripting"],
action: {
default_popup: "src/popup/index.html",
default_icon: {
"16": "public/icons/icon16.png",
"48": "public/icons/icon48.png",
},
},
background: {
service_worker: "src/background/index.ts",
type: "module",
},
content_scripts: [
{
matches: ["https://*/*"],
js: ["src/content/index.ts"],
css: ["src/content/styles.css"],
},
],
options_page: "src/options/index.html",
side_panel: { default_path: "src/sidepanel/index.html" },
icons: {
"16": "public/icons/icon16.png",
"48": "public/icons/icon48.png",
"128": "public/icons/icon128.png",
},
}));import manifest from "./manifest";
// ... crx({ manifest })/// <reference types="@crxjs/vite-plugin/client" />// background.ts — ?script gives you a resolved path for executeScript
import contentScript from "./content?script";
chrome.action.onClicked.addListener(async (tab) => {
await chrome.scripting.executeScript({
target: { tabId: tab.id! },
files: [contentScript],
});
});import mainWorldScript from "./inject?script&module";
await chrome.scripting.executeScript({
target: { tabId },
world: "MAIN",
files: [mainWorldScript],
});crx({
manifest,
browser: "chrome", // 'chrome' | 'firefox'
contentScripts: {
injectCss: true, // auto-inject CSS for content scripts
hmrTimeout: 5000, // HMR connection timeout (ms)
},
});# Start dev server (outputs to dist/ with HMR)
npm run dev
# 1. Open chrome://extensions
# 2. Enable "Developer mode"
# 3. Click "Load unpacked"
# 4. Select the dist/ directory
# 5. Edit code — popup/content scripts update instantly via HMR
# 6. Service worker changes trigger automatic extension reloadnpm run build # outputs to dist/cd dist && zip -r ../extension.zip .build: {
modulePreload: false;
}server: {
port: 5173,
strictPort: true,
hmr: { port: 5173 },
}my-extension/
├── src/
│ ├── background/
│ │ └── index.ts
│ ├── content/
│ │ ├── index.ts
│ │ └── styles.css
│ ├── popup/
│ │ ├── index.html <- CRXJS resolves HTML entry points
│ │ ├── App.tsx
│ │ └── main.tsx
│ ├── options/
│ │ ├── index.html
│ │ └── main.tsx
│ ├── sidepanel/
│ │ ├── index.html
│ │ └── main.tsx
│ └── shared/
│ ├── messages.ts
│ └── storage.ts
├── public/
│ └── icons/
├── manifest.ts <- or manifest.json
├── vite.config.ts
├── tsconfig.json
└── package.json