Definition:
"Extensions are small software programs that customize the browsing experience."
More detail:
"Google Chrome Extensions are applications that run inside the Chrome browser and provide additional functionality, integration with third party websites or services, and customized browsing experiences."
File type:
"Extension files are zipped into a single .crx package that the user downloads and installs."
Have a "single globally unique identified" ID
Made with:
Manifest.json
Built on web technologies such as HTML, JavaScript, and CSS
Assets like: audio, image ...
Every extension has a JSON-formatted manifest file, named manifest.json, that provides important information.
HTML is used as a content markup language, CSS is used for styling, and JavaScript for scripting
Chrome supports HTML5 and CSS3, developers can use the latest open web technologies such as canvas and CSS animations in their extensions
Capabilities:
Use 3rd party web services
Save data locally
Create UI outside of the rendered web page
Listen event on Chrome: click, switch tabs ...
...
Add an icon, tooltip, badge, and popup to the toolbar.
Add items to Google Chrome's context menu.
Create a version of the New Tab, Bookmark, or History page.