After reading the Get Started section, use this guide as an outline of extension components, their capabilities and how to combine them. First familiarize yourself with what extensions are capable of: Then learn how to combine these features using the extensions core concepts section.

Design the user interface

Most extensions need some kind of user interaction to work. The extensions platform provides a variety of ways to add interactions to your extension. These methods include popups triggered from the Chrome toolbar, side panels, context menus, and more.
Use the chrome.sidePanel API to host content in the browser's side panel alongside the main content of a web page.
Control the display of an extension's icon in the toolbar.
Add items to Google Chrome's context menu.
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Control the browser

Chrome's extension APIs make it possible to change the way your browser works.
Settings overrides are a way for extensions to override selected Chrome settings. Additionally, extensions can use HTML override pages to replace a page Google Chrome normally provides. An extension can override the bookmark manager, the history tab, or the new tab.
DevTools extensions add functionality to Chrome DevTools by accessing DevTools-specific extension APIs through a DevTools page added to the extension. You can also use the chrome.debugger API to invoke Chrome's remote debugging protocol. Attach to one or more tabs to instrument network interaction, debug JavaScript, mutate the DOM, and more.
The chrome.notifications API lets you create notifications using templates and show these notifications to users in the user's system tray.
Use the chrome.history API to interact with the browser's record of visited pages, and the chrome.browsingData API to manage other browsing data. Use chrome.topSites to access the most visited sites.
Use APIs such as chrome.tabs, chrome.tabGroups and chrome.windows to create, modify, and arrange the user's browser.
Use the chrome.commands API to add keyboard shortcuts that trigger actions in your extension. For example, you can add a shortcut to open the browser action or send a command to the extension.
Use the chrome.identity API to get OAuth 2.0 access tokens.
The chrome.management API provides ways to manage the list of extensions that are installed and running. It is particularly useful for extensions that override the built-in New Tab page.
The chrome.omnibox API allows you to register a keyword with Google Chrome's omnibox (address bar).
Use the chrome.privacy API to control usage of features in Chrome that can affect a user's privacy. Also see the chrome.proxy API to manage Chrome's proxy settings.
Use the chrome.downloads API to programmatically initiate, monitor, manipulate, and search for downloads.
Use the chrome.bookmarks API and the chrome.readingList API to create, organize, and otherwise manipulate these lists.

Control the web

Dynamically change the content and behavior of web pages. You can control and modify the web by injecting scripts, intercepting network requests, and using web APIs to interact with web pages.
Content scripts are files that run in the context of web pages. They use the standard Document Object Model (DOM), to read details of web pages the browser visits, make changes to them, and pass information to their parent extension.
The "activeTab" permission gives an extension temporary access to the currently active tab when the user invokes the extension, for example by clicking its action. Access to the tab lasts while the user is on that page, and is revoked when the user navigates away or closes the tab.
Use the chrome.declarativeNetRequest, chrome.webRequest and chrome.webNavigation APIs to observe, block, and modify network requests.
Learn about different approaches for recording audio and video from a tab, window, or screen using web platform APIs such as chrome.tabCapture or getDisplayMedia().
Use the chrome.contentSettings API to control whether websites can use features such as cookies, JavaScript, and plugins. More generally speaking, content settings allow you to customize Chrome's behavior on a per-site basis instead of globally.

Core concepts

Using web platform and extension APIs you can build more complex features by combining different UI components and extension platform features.
An extension service worker (service-worker.js) is an event-based script that the browser runs in the background. It is often used to process data, coordinate tasks in different parts of an extension, and as an extension's event manager.
Understand permissions: how they work and when to avoid asking for them when they're not needed.

Content filtering

There are different ways to implement content and network filtering in Chrome Extensions. Learn about the content filtering capabilities available to extensions and the different filtering approaches, techniques and APIs that can be used by Chrome Extensions.
Many times content scripts, or other extension pages, need to send or receive information from the extension service worker. In these cases, either side can listen for messages sent from the other end, and respond on the same channel.
Enable your extensions to exchange messages with native applications.
In Manifest V3 extensions need to bundle all code they are using inside the extension itself. There are different strategies for doing this.
Chrome Extensions have a specialized Storage API, available to all extension components. It includes four separate storage areas for specific use cases and an event listener that tracks whenever data is updated.
Service workers don't have DOM access. The Offscreen API allows the extension to use DOM APIs in a hidden document without interrupting the user experience by opening new windows or tabs.
Cross-origin isolation enables a web page to use powerful features such as SharedArrayBuffer. An extension can opt into cross-origin isolation by specifying the appropriate values for the "cross_origin_embedder_policy" and "cross_origin_opener_policy" manifest keys.
Learn how Chrome updates extensions update flow and how to monitor the distribution of extension updates.

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