The user does not have to remain connected to the Internet to execute the downloaded programs, because they execute from a locally maintained cache.Updates of the software download from the Web and become available when the user has a connection to the Internet, thus easing the burden of deployment.
Sun introduced version 1.0 of Web Start in March 2001,, computer administrators no longer have to install it separately.
Programmers often speak of the Java Network Launching Protocol (JNLP) interchangeably with the term "Web Start".
To reduce the size of a Java Web Start application Sun Microsystems introduced a compression system called Pack200 in Java 1.5.0.
It can compress a large jar file to one-ninth of its original size if it contains only Java classes.
Only signed applications can be configured to have additional permissions.
Web Start has an advantage over applets in that it overcomes many compatibility problems with browsers' Java plugins and different JVM versions.
The example below gives a simple JNLP file to launch the applet, specifying code base, source, main class and window size.
Such file contains all necessary references and is self-sufficient to launch the application.
Application designers can enable or disable this feature within JNLP files.
On slow connections Pack200 gives a performance boost in application startup time and download time.
The development of JNLP took place under the Java Community Process as JSR 56.