Editing Java applet (section)

== Technical information ==
Most browsers executed Java applets in a ''[[sandbox (security)|sandbox]]'', preventing applets from accessing local data like the [[file system]].<ref>{{Cite web|title=What Untrusted Java Code Can't Do|url=http://www.securingjava.com/chapter-two/chapter-two-2.html|access-date=2021-12-26|website=Securingjava.com|last1=McGraw|first1=Gary|last2=Felten|first2=Edward|year=1999}}</ref> The code of the applet was downloaded from a [[web server]], after which the browser either [[compound document|embedded]] the applet into a web page or opened a new window showing the applet's [[user interface]].

The first implementations involved downloading an applet class by class. While classes are small files, there are often many of them, so applets got a reputation as slow-loading components. However, since <code>[[JAR (file format)|.jar]]</code> files were introduced, an applet is usually delivered as a single file that has a size similar to an image file (hundreds of kilobytes to several megabytes).

Java [[Static library|system libraries]] and [[Runtime library|runtimes]] are backwards-compatible, allowing one to write code that runs both on current and on future versions of the Java virtual machine.

=== Similar technologies ===
Many Java developers, blogs and magazines recommended that the [[Java Web Start]] technology be used in place of applets.<ref>{{cite web |last1=Srinivas |first1=Raghavan N. |date=2001-07-06 |url=https://www.infoworld.com/article/2075391/java-web-start-to-the-rescue.html |title=Java Web Start to the rescue |work=[[JavaWorld]] |access-date=2020-07-13}}</ref> Java Web Start allowed the launching of unmodified applet code, which then ran in a separate window (not inside the invoking browser).

A [[Java Servlet]] is sometimes informally compared to be "like" a server-side applet, but it is different in its language, functions, and in each of the characteristics described here about applets.