Frequently Asked Questions

Contents

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2. API reference
   1. Properties
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   3. Events
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   4. Types
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General

What are Google Chrome Extensions?

Google Chrome Extensions are applications that run inside the Google Chrome browser and provide additional functionality, integration with third party websites or services, and customized browsing experiences.

What technologies are used to write extensions for Google Chrome?

Google Chrome Extensions are written using the same standard web technologies that developers use to create websites. HTML is used as a content markup language, CSS is used for styling, and JavaScript for scripting. Because Google Chrome supports HTML5 and CSS3, developers can use the latest open web technologies such as canvas and CSS animations in their extensions. Extensions also have access to several JavaScript APIs that help perform functions like JSON encoding and interacting with the browser.

Are extensions fetched from the web every time the browser is loaded?

Extensions are downloaded by the Google Chrome browser upon install, and are subsequently run off of the local disk in order to speed up performance. However, if a new version of the extension is pushed online, it will be automatically downloaded in the background to any users who have the extension installed. Extensions may also make requests for remote content at any time, in order to interact with a web service or pull new content from the web.

Development

How can I set up Google Chrome for extension development?

As long as you are using a version of Google Chrome that supports extensions, you already have everything you need to start writing an extension of your own. Select "Extensions" from the Tools menu (or from the window menu on Mac) and click "Developer Mode". From there, you can load an unpacked directory of files as if it were a packaged extension, reload extensions, and more. For a complete tutorial, please view this getting started guide.

Can I make cross-domain Ajax requests in an extension?

Yes. Extensions can make cross-domain requests. See this page for more information.

Can I use 3rd party web services in my extension?

Yes. Google Chrome Extensions are capable of making cross-domain Ajax requests, so they can call remote APIs directly. APIs which provide data in JSON format are particularly easy to use.

Can I use OAuth in my extensions?

Absolutely, there are extensions which use OAuth to access remote data APIs. Most developers find it convenient to use a JavaScript OAuth library in order to simplify the process of signing OAuth requests.

What UI controls can I create for my extension?

Extensions use HTML and CSS to define their user interfaces, so you can use standard form controls to build your UI, or style the interface with CSS, as you would a web page. Additionally, your extension may add buttons to the Google Chrome browser itself. See browser actions and page actions for more information.

Can I load DLLs in my extension?

Yes, using the NPAPI interface. Because of the possibility for abuse, though, we will review your extension before hosting it in the Google Chrome Extensions gallery.

Can Google Chrome Extensions encode/decode JSON data?

Yes, because V8 (Google Chrome's JavaScript engine) supports JSON.stringify and JSON.parse natively, you may use these functions in your extensions as described here without including any additional JSON libraries in your code.

Can I store data locally in my extension?

Yes, extensions can use localStorage to store string data permanently. Using Google Chrome's built-in JSON functions, you can store complex data structures in localStorage. For extensions which have the need to execute SQL queries on their stored data, Google Chrome implements client side SQL databases which may be used as well.

How much data can I store in localStorage?

Extensions can store up to 5MB of data in localStorage.

Can I create an options menu for my application?

You can let users set options for your extension by creating an options page which is a simple HTML page that will be loaded when a user clicks the "options" button for your extension. This page can read and write settings to localStorage, or even send options to a web server so that they can be persisted across browsers.

Can two extensions communicate with each other?

Extensions may pass messages to other extensions. See the message passing documentation for more information.

What debugging tools are available to extension developers?

Google Chrome's built-in developer tools can be used to debug extensions as well as web pages. See this tutorial on debugging extensions for more information.

Can extensions use Google Analytics?

Yes, since extensions are built just like websites, they can use Google Analytics to track usage.