> ## Documentation Index
> Fetch the complete documentation index at: https://extension.js.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Extension.js features overview

> Explore core Extension.js capabilities including cross-browser builds, config files, HMR reload behavior, path resolution, and telemetry controls.

Understand the core platform capabilities that make Extension.js practical for real-world browser extension development.

## Feature chooser

| Goal                                           | Start here                                                                    |
| ---------------------------------------------- | ----------------------------------------------------------------------------- |
| Ship one codebase to multiple browsers         | [Cross-browser compatibility](/docs/features/cross-browser-compatibility)     |
| Handle browser-specific manifest differences   | [Browser-specific manifest fields](/docs/features/browser-specific-fields)    |
| Keep non-manifest assets organized             | [Special folders](/docs/features/special-folders)                             |
| Manage environment-specific behavior           | [Environment variables](/docs/features/environment-variables)                 |
| Centralize build/runtime defaults              | [Extension configuration](/docs/features/extension-configuration)             |
| Extend bundler behavior safely                 | [Rspack configuration](/docs/features/rspack-configuration)                   |
| Understand update behavior in development mode | [Page reload and hot module replacement (HMR)](/docs/features/reload-and-hmr) |
| Avoid path drift between source and output     | [Path resolution](/docs/features/path-resolution)                             |
| Build and package for target matrices          | [Multi-platform builds](/docs/features/multi-platform-builds)                 |
| Review the telemetry privacy contract          | [Telemetry and privacy](/docs/features/telemetry-and-privacy)                 |

## Recommended progression

1. Validate browser output guarantees (`cross-browser-compatibility`).
2. Lock project defaults (`extension-configuration`).
3. Add advanced behavior (`rspack-configuration`, `environment-variables`).
4. Optimize release flows (`multi-platform-builds`).

## Video walkthrough

## Next steps

* Apply these capabilities in [Workflows](/docs/workflows/index).
* Choose the right execution command in [Commands reference](/docs/commands/index).
* Review the privacy contract in [Telemetry and privacy](/docs/features/telemetry-and-privacy).