browser-extension-capabilities

A lightweight, zero-dependency TypeScript library for analyzing browser extension manifests and extracting their capabilities. Useful for extension development tools, analysis tools, and browser extension marketplaces.

What are Browser Extension Capabilities?

Browser extension capabilities represent the functional interfaces and execution environments that an extension can utilize. These are the different ways an extension can interact with the browser, web pages, and users. Each capability corresponds to specific manifest fields and defines where and how the extension's code can run.

For example:

Background Capability: Allows the extension to run persistent code in the background
Content Scripts Capability: Enables the extension to interact with web page content
Popup Capability: Provides a user interface through browser toolbar buttons
Options Capability: Offers configuration pages for user settings

Features

Comprehensive Detection: Detects all major browser extension capabilities and interfaces
User-Friendly Output: Returns descriptive capability objects with explanations
Cross-Browser Support: Works with Chrome, Firefox, Edge, and other Chromium-based browsers

Installation

npm install browser-extension-capabilities

Usage

import { getExtensionCapabilities } from 'browser-extension-capabilities'

// Analyze an extension directory
const capabilities = getExtensionCapabilities('./path/to/extension')

// Returns array of capability objects
console.log(capabilities)
// [
//   {
//     capability: "background",
//     description: "Background service worker or page for persistent functionality"
//   },
//   {
//     capability: "content_scripts",
//     description: "Content scripts that run on web pages to interact with page content"
//   },
//   {
//     capability: "popup",
//     description: "Browser action popup or toolbar button functionality"
//   }
// ]

Supported Capabilities

Capability	Description	Manifest Fields
background	Background service worker or page for persistent functionality	`background.page`, `background.scripts`, `background.service_worker`
content_scripts	Content scripts that run on web pages to interact with page content	`content_scripts`
popup	Browser action popup or toolbar button functionality	`action.default_popup`
sidebar	Side panel interface for additional extension features	`side_panel.default_path`, `sidebar_action.default_panel`
devtools	Developer tools panel for debugging and development	`devtools_page`
options	Extension options page for user configuration	`options_ui.page`
newtab	Custom new tab page replacement	`chrome_url_overrides.newtab`
bookmarks	Custom bookmarks page replacement	`chrome_url_overrides.bookmarks`
history	Custom history page replacement	`chrome_url_overrides.history`
sandbox	Sandboxed pages with restricted permissions for security	`sandbox.pages`
web_resources	Web accessible resources for content script communication	`web_accessible_resources`

API Reference

`getExtensionCapabilities(dataDir: string): ExtensionCapability[]`

Analyzes a browser extension manifest and returns an array of capability objects.

Parameters

dataDir (string): Directory path containing the extension's manifest.json file

Returns

ExtensionCapability[]: Array of capability objects with capability and description properties

Example

import { getExtensionCapabilities } from 'browser-extension-capabilities'

try {
  const capabilities = getExtensionCapabilities('./my-extension')

  capabilities.forEach(({ capability, description }) => {
    console.log(`${capability}: ${description}`)
  })
} catch (error) {
  console.error('Failed to analyze extension:', error)
}

Types

interface ExtensionCapability {
  capability: string
  description: string
}

Error Handling

The library gracefully handles various error scenarios:

Missing manifest file: Returns [{ capability: "manifest", description: "Basic extension manifest configuration" }]
Invalid JSON: Returns fallback capability with error logging
Malformed manifest: Attempts to extract available capabilities and falls back gracefully

Use Cases

Extension Analysis Tools: Analyze extension capabilities and permissions
Marketplace Validation: Verify extension capabilities for store listings
Development Tools: IDE plugins and development utilities
Security Analysis: Understand extension execution environments
Documentation Generation: Auto-generate extension documentation

Browser Support

✅ Chrome/Chromium (Manifest V2 & V3)
✅ Firefox (WebExtensions)
✅ Edge (Chromium-based)
✅ Opera (Chromium-based)
✅ Safari (WebExtensions)

License

MIT (c) Cezar Augusto