CHAPTER 1 ■ INTRODUCTION TO GOOGLE CHROME EXTENSIONS
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web browser are compatible with the Opera web browser, ever since Opera shifted to the
Chromium’s extension model (after Opera dropped its own Presto engine, in favor of the
WebKit engine used by the Google Chrome web browser, from the Chromium project).
Developing extensions for the Safari web browser has a similar learning curve to that
of the Google Chrome web browser, and developing extensions for both is easy because it
does not require you to learn any newer technologies (only existing web technologies are
used). But developing extensions for the Firefox web browser is comparatively difficult
as it involves the use of technologies apart from web technologies, such as XUL, XPCOM,
etc. (you can read more about these at
https://en.wikipedia.org/wiki/Add-on_
(Mozilla)#Extension_technologies
). This book only covers development of extensions
on the Google Chrome web browser.
■ Note The Chrome Web Store is an online marketplace where users can browse for
Chrome apps, extensions, and themes. The store helps users find, purchase, and install
content on the Chrome browser.
Extensions Are Not Plug-ins
An important point to note is that browser extensions are different from browser plug-
ins . While browser extensions are sandboxed within the host web browser (software),
plug-ins are not. Here, a sandbox can be thought of as a software container – allowing the
execution of web technologies, and at the same time providing access to the features of
browsers, such as tabs, history, buttons, popups, etc.
In addition to this, extensions add new functionality(ies) to browsers by combining
existing features that are already available on browsers (in case of Chrome Extensions,
this is done using the API provided by the Extensions framework). Plug-ins, however,
provide new functionality(ies) by providing support for particular media types to
browsers. In the former case, the example could be an extension that allows users to save
all the opened tabs that are not in incognito mode, to the local storage. For the latter
case, the example could be a plug-in that allows reading and rendering of PDF files on
the browser.
Also note that there is another kind of web application that developers can create
for the Chrome browser. These applications are known as Google Chrome Apps . From
a development’s standpoint, Google Chrome Apps are somewhere in between Google
Chrome Extensions and browser plug-ins.
This book does not discuss developing Google Chrome Apps, as it only targets the
development of Google Chrome Extensions. But keep in mind that developing Chrome
Apps is very similar to developing extensions for the Chrome browser. If you want to
know more about Google Chrome Apps, you can visit the following URLs:
•
https://en.wikipedia.org/wiki/Google_Chrome_Apps
•
https://developer.chrome.com/apps/about_apps
•
http://stackoverflow.com/questions/tagged/google-chrome-app
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