Previous | Next | Trail Map | Writing Applets | Overview of Applets

What Applets Can and Can't Do

This page gives an overview of both the restrictions applets face and the special capabilities they have. You'll find more details in the Understanding Applet Capabilities and Restrictions(in the Writing Applets trail) lesson.

Security Restrictions

Every browser implements security policies to keep applets from compromising system security. This section describes the security policies that current browsers adhere to. However, the implementation of the security policies differs from browser to browser. Also, security policies are subject to change. For example, if a browser is developed for use only in trusted environments, then its security policies will likely be much more lax than those described here.

Current browsers impose the following restrictions on any applet that is loaded over the network:

Each browser has a SecurityManager object that implements its security policies. When a SecurityManager detects a violation, it throws a SecurityException. Your applet can catch this SecurityException and react appropriately.

Applet Capabilities

The java.applet package provides an API that gives applets some capabilities that applications don't have. For example, applets can play sounds, which other programs can't do yet.

Here are some other things that current browers and other applet viewers let applets do:

Previous | Next | Trail Map | Writing Applets | Overview of Applets