Overview

The applets are used to provide interactive features to web applications that cannot be provided by HTML alone. They can capture mouse input and also have controls like buttons or check boxes. In response to user actions, an applet can change the provided graphic content. This makes applets well-suited for demonstration, visualization, and teaching. There are online applet collections for studying various subjects, from physics to heart physiology.

An applet can also be a text area only; providing, for instance, a cross-platform command-line interface to some remote system. If needed, an applet can leave the dedicated area and run as a separate window. However, applets have very little control over web page content outside the applet's dedicated area, so they are less useful for improving the site appearance in general, unlike other types of browser extensions (while applets like news tickers or WYSIWYG editors are also known). Applets can also play media in formats that are not natively supported by the browser. Pages coded in HTML may embed parameters within them that are passed to the applet. Because of this, the same applet may have a different appearance depending on the parameters that were passed.

As applets were available before CSS and DHTML were standard, they were also widely used for trivial effects such as rollover navigation buttons. This approach, which posed major problems for accessibility and misused system resources, is no longer in use and was strongly discouraged even at the time.