Opera widgets are web applications that run directly on your desktop without displaying the browser controls because Opera web browser can install and show them automatically.
They can be constructed using regular client side programming languages such as JavaScript and Flash. As a consequence, minimal knowledge regarding common used web-related programming languages are necessary if you want to create a new widget or to modify an existing one.

The main parts of an Opera widget are a file named index.html and a config.xml file. The index.html file can control external files, such as Flash animations or external Javascripts or could contain a Javascript in it, for example. Practically a widget could be assimilated to a regular client side web application which performs certain actions on a Windows or Linux desktop, as if it was called from a web browser. (more…)