@samrum/vite-plugin-web-extension

Generate cross browser platform, ES module based web extensions.

Manifest V2 & V3 Support
Completely ES module based extensions
- Including in content scripts!
Vite based html and static asset handling
- Including in content scripts!
HMR support
- All Manifest entry points
  - Including content scripts when using a Chromium browser!
- CSS styles in content scripts
  - Including shadow DOM rendered content!
- Including Manifest V3 support since Chromium 110!

Quick Start

Create a new Vite web extension project

npm init @samrum/vite-plugin-web-extension@latest

Supports choice of Manifest version, TypeScript support, and framework (Preact, React, Solid, Svelte, Vanilla, Vue).

Check the README of the generated extension for usage information.

Usage

Requires Vite 3+

npm install @samrum/vite-plugin-web-extension

Examples

Manifest V2

vite.config.js:

import { defineConfig } from "vite";
import webExtension from "@samrum/vite-plugin-web-extension";

export default defineConfig({
  plugins: [
    webExtension({
      manifest: {
        name: pkg.name,
        description: pkg.description,
        version: pkg.version,
        manifest_version: 2,
        background: {
          scripts: ["src/background/script.js"],
        },
      },
    }),
  ],
});

Manifest V3

vite.config.js:

import { defineConfig } from "vite";
import webExtension from "@samrum/vite-plugin-web-extension";

export default defineConfig({
  plugins: [
    webExtension({
      manifest: {
        name: pkg.name,
        description: pkg.description,
        version: pkg.version,
        manifest_version: 3,
        background: {
          service_worker: "src/background/serviceWorker.js",
        },
      },
    }),
  ],
});

Firefox Experimental Manifest V3

There are two configurations an extension needs to make for experimental manifest V3 support:

Background service workers are not supported, so you are required to use a background script.
The use_dynamic_url property is not supported for web accessible resources. In the plugin options, set useDynamicUrlWebAccessibleResources to false:
```
  webExtension({
    ...
    useDynamicUrlWebAccessibleResources: false,
  }),
```

Devtools

To add content to the browser dev tools, add `devtools_page` to your manifest

devtools_page: "src/entries/devtools/index.html",

Place a script devtools.js in public dir.

var _browser;
if (chrome) {
  _browser = chrome;
} else {
  _browser = browser;
}
_browser.devtools.panels.create(
  "My Panel", // title
  "images/icon-16.png", // icon
  "src/entries/devtools/index.html" // content
);

Then load the script from your devtools html which placed in src/entries/devtools/index.html.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Devtools</title>
  </head>
  <body>
    <div id="app"></div>
    <script type="module" src="./main.ts"></script>
    <script src="/devtools.js"></script>
  </body>
</html>

Options

manifest

The manifest definition for your extension
All manifest property file names should be relative to the root of the project.

useDynamicUrlWebAccessibleResources (optional)

Type: boolean
Default: false
Adds the use_dynamic_url property to web accessible resources generated by the plugin
- Caution: In Chrome 130, with this option enabled, importing a generated resource using chrome.runtime.getURL will not work (Chromium Issue)l

optimizeWebAccessibleResources (optional)

Type: boolean
Default: true
On build, in Manifest V3, merge web accessible resource definitions that have matching non-resource properties and dedupe and sort resources. In Manifest V2, sort web accessible resources.

additionalInputs (optional)

Type:

  type AdditionalInput =
    | string
    | {
        fileName: string;
        webAccessible?:
          | boolean
          | {
              matches: string[];
              extensionIds?: string[];
              excludeEntryFile?: boolean;
            }
          | {
              matches?: string[];
              extensionIds: string[];
              excludeEntryFile?: boolean;
            };
      };

  additionalInputs?: {
    scripts?: AdditionalInput[];
    html?: AdditionalInput[];
    styles?: AdditionalInput[];
  };

Additional input files that should be processed and treated as web extension inputs.
Useful for dynamically injected scripts or dynamically opened HTML pages.
The webAccessible option configures whether the input file and its dependencies are included in the manifest web_accessible_resources property. Defaults to true.
- When set to true, defaults to:
```
  {
    matches: ['<all_urls>'],
    excludeEntryFile: false,
  }
```
- The excludeEntryFile option prevents the entry file from being added as a web accessible resource. Defaults to false.

Example

  webExtension({
    manifest: ...,
    additionalInputs: {
      scripts: [
        'src/entries/webAccessibleScript.js', // defaults to webAccessible: true
        {
          fileName: 'src/entries/webAccessibleScript2.js',
          webAccessible: true,
        },
        {
          fileName: 'src/entries/privateScript.js', // entry file and dependencies are not web accessible
          webAccessible: false,
        },
        {
          fileName: 'src/entries/entryFileExcluded.js', // entry file is not web accessible and dependencies are
          webAccessible: {
            matches: ['<all_urls>'],
            excludeEntryFile: true,
          },
        },
      ],
    },
  })

Content Scripts

For HMR style support within shadow DOMs, use the addStyleTarget function to add the shadowRoot of your element as a style target:

if (import.meta.hot) {
  const { addViteStyleTarget } = await import(
    "@samrum/vite-plugin-web-extension/client"
  );

  await addViteStyleTarget(appContainer);
}

For builds, use the import.meta.PLUGIN_WEB_EXT_CHUNK_CSS_PATHS variable to reference an array of CSS asset paths associated with the current output chunk.

TypeScript

In an env.d.ts file, add the following type reference to define the plugin specific import.meta variables as well as plugin client functions:

/// <reference types="@samrum/vite-plugin-web-extension/client" />

Browser Support

The following requirements must be met by the browser:

Must support dynamic module imports made by web extension content scripts.
Must support import.meta.url

A sample of supported browsers:

	Manifest V2	Manifest V3
Chromium	64	91
Firefox	89	N/A (In development)

The plugin will automatically default vite's build.target config option to these minimum browser versions if not already defined by the user.

For dev mode support in Manifest V3, Chromium version must be at least 110.

How it works

The plugin will take the provided manifest, generate rollup input scripts for supported manifest properties, then output an ES module based web extension.

This includes:

Generating and using a dynamic import wrapper script in place of original content scripts. Then, moving the original scripts to web_accessible_resources so they are accessible by the wrapper script. Needed because content scripts are not able to be loaded directly as ES modules.
- This may expose your extension to fingerprinting by other extensions or websites. Manifest V3 supports a use_dynamic_url property that will mitigate this. This option is set for manifest V3 web accessible resources generated by this plugin.
Modifying Vite's static asset handling to maintain import.meta.url usages instead of rewriting to self.location. Needed so content script static asset handling can function correctly.
Modifying Vite's HMR client to add support for targeting specific elements as style injection locations. Needed to support HMR styles in shadow DOM rendered content.

Why this is a Vite specific plugin

The plugin relies on Vite to parse and handle html files in addition to relying on Vite's manifest generation in order to map generated files to the eventual extension manifest.

Development

This project uses pnpm for package management.

Lint

pnpm lint

Tests

pnpm test

Build

pnpm build