In addition to the chrome.* APIs, extensions can use all the APIs that the browser provides to web pages and apps. If the browser doesn't support an API you want to use, you can bundle additional API libraries into your extension.

Here's a sampling of the APIs that extensions can use:

Standard JavaScript APIs

These are the same core JavaScript and DOM APIs that you can use in ordinary web apps. [PENDING: check! should link to complete list]

XMLHttpRequest

Use XMLHttpRequest to request data from one or more servers. The permissions field of the manifest specifies which hosts the extension can send requests to.

WebKit APIs

Because Google Chrome is built upon WebKit, your extensions can use WebKit APIs. Especially useful are the experimental CSS features such as filters, animations, and transformations. Here's an example of using WebKit styles to make the UI spin:

<style>
  div:hover {
    -webkit-transform: rotate(360deg);
    -webkit-transition: all sl ease-out;
  }
</style>

[PENDING: link to complete list of webkit apis]

V8 APIs, such as JSON

Because JSON is in V8, you don't need to include a JSON library to use JSON functions. [PENDING: what other APIs are in v8? link to complete list]

HTML5 APIs, such as localStorage

HTML5 is still being defined and implemented, but Google Chrome already supports local storage, which extensions can use to store data. [PENDING: Other important API? link to complete list]

APIs in bundled libraries

If you want to use a library that the browser doesn't provide (for example, jQuery), you can bundle that library's JavaScript files with your extension. Bundled libraries work in extensions just as they would in any other web pages.