Configuration

ExtForge reads its config from extforge.config.ts (or .js / .mjs) in the project root. The file must export a default config object — use defineConfig for TypeScript inference.

import { defineConfig } from 'extforge';

export default defineConfig({
  browsers: ['chrome', 'firefox'],
  framework: 'react',
  css: 'tailwind',
  manifest: {
    name: 'My Extension',
    version: '1.0.0',
    // ...
  },
});

defineConfig is an identity function — it returns the object unchanged but gives your editor full TypeScript autocompletion.

`framework`

Type: 'react' | 'vanilla'
Default: 'react'

Setting framework drives automatic plugin injection. When framework: 'react', ExtForge injects presetReact() before any user plugins so all entry points get the correct JSX transform without extra configuration.

export default defineConfig({
  framework: 'react', // presetReact() injected automatically
});

See preset-react for the options you can pass if you need to override the defaults (e.g. Preact or classic runtime).

`css`

Type: 'tailwind' | 'vanilla' | 'none'
Default: 'tailwind'

css: 'tailwind' scaffolds a postcss.config.js and tailwind.config.js and assumes Tailwind is installed. It does not inject a Tailwind plugin itself — PostCSS handles that at esbuild’s CSS entry point. Set 'vanilla' to opt out of any preset but keep the CSS pipeline. Set 'none' to disable CSS processing entirely.

`browsers`

Type: Array<'chrome' | 'firefox' | 'edge' | 'safari'>
Default: ['chrome', 'firefox']

Declares which browsers to build for. extforge build iterates this list and produces a separate output under dist/<browser>/. extforge dev defaults to chrome; pass --browser firefox to target a different browser in dev mode.

export default defineConfig({
  browsers: ['chrome', 'firefox', 'edge', 'safari'],
});

Each browser gets its own manifest generated from the shared manifest config plus any per-browser overrides. Duplicate entries are deduplicated automatically.

See /reference/config/browsers/ for the full spec.

`manifest`

The manifest object maps to the Manifest V3 fields ExtForge understands. ExtForge generates the final manifest.json from this config — you never write manifest.json by hand.

See /reference/config/manifest/ for the complete field list.

`name` and `version`

manifest: {
  name: 'My Extension',
  version: '1.0.0',
  description: 'Does something useful.',
}

version must be a dot-separated integer string (e.g. 1.2.3 or 1.2.3.4 for Chrome’s four-part format).

`action` (popup)

manifest: {
  action: {
    defaultPopup: 'src/ui/popup/popup.html',
    defaultTitle: 'My Extension',
  },
}

`sidePanel`

manifest: {
  sidePanel: {
    defaultPath: 'src/ui/sidepanel/sidepanel.html',
  },
}

sidePanel is Chrome/Edge-only. If you list Firefox in browsers, ExtForge omits the side_panel key from that browser’s manifest automatically. Use a per-browser override if you want a fallback popup on Firefox.

`optionsPage`

manifest: {
  optionsPage: 'src/ui/options/options.html',
}

`background.serviceWorker`

manifest: {
  background: {
    entrypoint: 'src/background/index.ts',
  },
}

ExtForge emits service_worker on Chrome/Edge/Safari and scripts on Firefox (MV3). You do not need a per-browser override for this field — the manifest generator handles it using the browser capability matrix. See the cross-browser guide for details.

`contentScripts`

An array of content script declarations. Each entry maps to a content_scripts object in the generated manifest.

manifest: {
  contentScripts: [
    {
      matches: ['https://*.example.com/*'],
      js: ['src/content/index.ts'],
      css: ['src/content/style.css'],
      runAt: 'document_idle',
    },
  ],
}

runAt accepts 'document_start', 'document_end', or 'document_idle'.

`webAccessibleResources`

manifest: {
  webAccessibleResources: [
    {
      resources: ['assets/*'],
      matches: ['https://*.example.com/*'],
    },
  ],
}

`permissions`

manifest: {
  permissions: {
    required: ['storage', 'activeTab', 'scripting'],
    optional: ['tabs'],
    host: ['https://*.example.com/*'],
  },
}

required permissions are listed under permissions in the manifest. optional maps to optional_permissions. host patterns go under host_permissions (MV3).

The full permission list is in /reference/config/manifest/.

Per-browser manifest overrides

Use manifest.browserOverrides to merge browser-specific fields into the generated manifest. Overrides are shallow-merged over the base manifest.

manifest: {
  background: {
    entrypoint: 'src/background/index.ts',
  },
  browserOverrides: {
    firefox: {
      firefoxId: 'my-extension@example.com',
    },
    safari: {
      // Safari doesn't support sidePanel; nothing to override here —
      // ExtForge omits it automatically.
    },
  },
}

See cross-browser guide for common override patterns.

`build`

build: {
  outDir: 'dist',       // output root; per-browser dirs land under here
  srcDir: 'src',        // source root for resolving relative paths
  sourcemap: false,     // generate source maps (true in dev)
  esbuild: {            // pass-through to esbuild BuildOptions
    target: 'es2020',
    define: { 'process.env.NODE_ENV': '"production"' },
  },
}

esbuild is a free-form object that merges into every esbuild invocation. Use it for define, target, external, minify, or any other esbuild option. Plugin hooks can override per-entry options via onBuildEntry.

See /reference/config/build/ for all fields.

`dev`

dev: {
  port: 35729,          // HMR WebSocket port
  host: 'localhost',    // HMR host
  debounce: 150,        // file-change debounce in ms
  open: false,          // open browser on start
  strictCompat: false,  // treat compat warnings as errors in dev
}

debounce controls how long ExtForge waits after the last file change before triggering a reload. Raising it can help if file writes trigger multiple events in quick succession.

See /reference/config/dev/ and the HMR guide.

`plugins`

plugins: [
  myPlugin(),
  anotherPlugin({ option: true }),
]

User plugins are appended after built-in plugins. The framework preset (presetReact(), etc.) always runs first.

See the plugins guide for writing plugins, or /reference/plugins/api/ for the hook reference.

Worked example

A config for an extension with a popup, a content script, a side panel, and two browser targets:

import { defineConfig } from 'extforge';

export default defineConfig({
  browsers: ['chrome', 'firefox'],
  framework: 'react',
  css: 'tailwind',

  manifest: {
    name: 'Page Annotator',
    version: '1.0.0',
    description: 'Annotate any web page.',

    action: {
      defaultPopup: 'src/ui/popup/popup.html',
      defaultTitle: 'Page Annotator',
    },

    sidePanel: {
      defaultPath: 'src/ui/sidepanel/sidepanel.html',
    },

    background: {
      entrypoint: 'src/background/index.ts',
    },

    contentScripts: [
      {
        matches: ['<all_urls>'],
        js: ['src/content/index.ts'],
        css: ['src/content/style.css'],
        runAt: 'document_idle',
      },
    ],

    permissions: {
      required: ['storage', 'activeTab', 'scripting', 'sidePanel'],
      optional: ['tabs'],
      host: [],
    },

    webAccessibleResources: [
      {
        resources: ['assets/*'],
        matches: ['<all_urls>'],
      },
    ],

    browserOverrides: {
      firefox: {
        // Firefox does not support sidePanel; provide a fallback action popup
        action: {
          defaultPopup: 'src/ui/sidepanel/sidepanel.html',
          defaultTitle: 'Page Annotator',
        },
        firefoxId: 'page-annotator@example.com',
      },
    },
  },

  build: {
    outDir: 'dist',
    srcDir: 'src',
    sourcemap: false,
    esbuild: {
      target: 'es2020',
    },
  },

  dev: {
    port: 35729,
    debounce: 150,
  },
});

Config resolution order

extforge.config.ts (or .js / .mjs) is loaded from the project root.
Default values fill in missing fields.
The Zod schema validates the result; unknown keys are passed through (passthrough()).
Built-in plugins (presetReact(), etc.) are prepended to the plugin list.
onConfigResolved hooks from all plugins fire.

If the config file is missing, loadExtForgeConfig falls back to the defaults and logs a warning. It does not error unless EXTFORGE_STRICT_CONFIG=1 is set.

Configuration

framework

css

browsers

manifest

name and version

action (popup)

sidePanel

optionsPage

background.serviceWorker

contentScripts

webAccessibleResources

permissions