Definition
Applets are small applications designed to perform specific tasks within a larger program or environment. Historically, applets were most associated with Java, where they were embedded in web pages and executed inside a browser through the Java Virtual Machine. Their purpose was to deliver interactive features such as animations, calculators, or simple games.
Applets provided a way to run cross-platform applications inside a browser, but over time, they became less common due to security risks and modern alternatives such as JavaScript, HTML5, and mobile apps.
Advanced
At an advanced level, applets operate within a sandboxed environment, restricting access to system resources for security. Java applets, for example, required a browser plug-in and could use signed certificates for elevated permissions.
Although rarely used in modern web development, applets remain relevant in legacy enterprise systems and educational environments. They illustrate early efforts to create portable, modular, and lightweight software components.
Why it matters
- Introduced the concept of modular, reusable applications within browsers.
- Allowed businesses to add interactivity before modern frameworks existed.
- Still used in some industries where legacy systems remain in operation.
- Influenced the evolution of client-side web technologies.
Use cases
- Embedding interactive charts or simulations in educational websites.
- Running lightweight tools such as calculators or file uploaders.
- Supporting legacy enterprise applications with embedded Java tools.
- Demonstrating modular programming concepts in computer science education.
Metrics
- Load time and responsiveness of the applet.
- Compatibility across browsers and platforms.
- Security vulnerabilities and patch status.
- User adoption and reliance on legacy systems.
Issues
- Browser plug-in support for Java applets has been deprecated.
- Security vulnerabilities made them targets for malware.
- Poor performance compared to modern frameworks.
- Limited support and maintenance for legacy systems.
Example
In the early 2000s, universities used Java applets to deliver interactive physics simulations. These tools allowed students to visualise experiments directly in the browser, improving learning outcomes. Today, such tools are replaced by HTML5 applications.