An applet (little application) is a small software program that supports a larger application program. In the past, the term applet was often associated with the Java programming language. Today, the term is often associated with If This Then That (IFTTT), a no-code/low-code software tool for creating small programs composed of triggers (If This) and actions (Then That).
History of Java applets
Sun Microsystems introduced Java applets in 1995. Unlike other applications, Java applets could not be run directly by the operating system. Instead, they had to run within the Java Runtime Environment (JRE) or within another program that included a Java plug-in. Because Java applets ran within the JRE and were not executed by the operating system, they could run on Windows, Mac and Linux systems.
This cross-platform capability made applets useful to web developers who wanted to add functionalities on a webpage that hypertext markup language (HTML) could not provide. In the early days of the internet, applets were commonly used to create interactive buttons, check boxes, forms and other small animations on websites. To accommodate the use of applets, HTML4 included an <applet> tag. The tag invoked a Java virtual machine (JVM) plugged into the browser and was accompanied by <parameters> that specified where and how the applet should display on the webpage.
Plug-ins offered a way to bring advanced capabilities to the browser environment without forcing users to install applications locally. If an end user's browser couldn't run Java, it would either skip over the <applet> tag or display alternate text, which typically explained to the end user what the applet required to run. The applet tag was replaced by <embed> and <object> tags in HTML5.
When a browser launched a Java applet from a webpage, the applet executed within a JVM, an environment not controlled by browser developers. This proved to be frustrating for both developers and end users, as plug-ins increasingly became targets for security exploits, which in turn, required Java to be updated frequently. By 2015, most browser vendors had either removed or announced their intentions to remove Java plug-in support. In response, Oracle deprecated the Java browser plug-in in Java Development Kit 9 in favor of installable applications or alternative technologies such as Java Web Start.
IFTTT is an online service for creating simple conditional statements. Formerly, these statements were known as recipes, but today they are referred to as applets. IFTTT uses common programming logic to allow certain events triggered by one software as a service to cause a reaction in another cloud service. This allows a nontechnical end user to automate everyday tasks by programming these triggers and actions. For example, an office manager could create an applet to have Amazon Echo's Alexa switch off lights when the front door is locked.