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

# Extension Types

> Learn the main types of Chrome extensions, when to use each one, and how Extensy combines them based on your prompt.

Chrome extensions are not one-size-fits-all. They can live in different parts of the browser depending on what they need to do. Understanding the main types helps you describe your goal to Extensy clearly — or just gives you context for what gets built when you submit a prompt.

## Popup extensions

The most common type. A popup extension adds an icon to your Chrome toolbar. When you click the icon, a small window appears with your extension's UI.

* **Best for**: Utilities, quick-action tools, dashboards, and calculators.
* **Example prompt**: "Build a unit converter popup that switches between miles and kilometers."

## Content script extensions

These extensions inject JavaScript (and optionally CSS) directly into the webpages you visit. Your code runs inside the page's context and can read or modify the DOM.

* **Best for**: Page enhancers, scrapers, UI modifiers, and ad blockers.
* **Example prompt**: "Build a Chrome extension that highlights every price on a webpage in green."

## Background service worker extensions

These extensions run their logic silently in the background using a service worker. They have no visible UI of their own but respond to browser events like tab changes, alarms, or incoming messages.

* **Best for**: Trackers, sync tools, scheduled tasks, and network monitors.
* **Example prompt**: "Build an extension that checks a specific API every 10 minutes and shows a desktop notification when there's a new post."

## Options page extensions

If your extension has many settings, a dedicated options page opens in its own full browser tab. This gives users space to configure complex preferences without the size constraints of a popup.

* **Best for**: Highly configurable tools, advanced dashboards, and power-user settings.
* **Example prompt**: "Build an extension with an options page where I can save my name, pre-fill my email address, and pick a custom color theme."

## Sidebar panel extensions

Introduced in Chrome 114, side panel extensions live in Chrome's built-in Side Panel. The panel stays open as you navigate between tabs, making it ideal for persistent companions.

* **Best for**: AI assistants, research tools, note-taking apps, and vertical dashboards.
* **Example prompt**: "Build a Chrome extension with a persistent side panel where I can save research snippets from any site I visit."

## DevTools extensions

These extensions add a custom panel directly inside Chrome's Developer Tools (`Inspect` window). They are primarily aimed at developers building or debugging web applications.

* **Best for**: Debugging tools, custom consoles, state inspectors, and API monitors.
* **Example prompt**: "Build a DevTools panel that shows me all `localStorage` keys and values for the current page."

## Choosing the right type

| Your goal | Best extension type |
| :- | :- |
| Quick utility or dashboard | Popup |
| Modify or enhance a webpage | Content script |
| Periodic tasks or background logic | Background service worker |
| Many user-configurable settings | Options page |
| Persistent, always-visible helper | Sidebar panel |
| Developer tooling | DevTools extension |

> [!NOTE]
>
> You don't have to pick just one type. Extensy can combine multiple types — for example, a popup that controls a content script — into a single cohesive extension based on your prompt.

> [!TIP]
>
> If you're unsure which type you need, describe what you want the extension to do in plain English. Extensy will automatically select the best combination of files and components for your use case.


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