Why convert JNLP to JAR?
Java Web Start was removed from Java 11 in 2018, so the normal JNLP launch path no longer works on modern Java. A JNLP file is a small XML application-launch descriptor - the actual application code lives in JAR files hosted on a remote server. Downloading those JARs lets you inspect or attempt to run the application without a Java Web Start implementation.
How to convert JNLP to JAR
Notepad FREE
Open the .jnlp in Notepad or any text editor, locate the codebase attribute and each <jar href> entry, then download each JAR from the combined URL using a browser.
OpenWebStart FREE
Install OpenWebStart and open the .jnlp file with it; it downloads the JARs into a local cache folder from which you can copy them.
About these formats
.JNLP
Java Network Launch Protocol file
A JNLP file is a small XML launcher for Java Web Start that tells Java which application JAR files to download from a server and run. The technology is discontinued. Oracle removed Java Web…
Open .JNLP details →
.JAR
Java Archive
A JAR file is a Java Archive - a ZIP bundle of compiled Java bytecode (.class files), resources, and a manifest. To run an executable JAR you need Java installed (OpenJDK/Temurin is free),…
Open .JAR details →Quality & what to watch
- A JNLP file is typically 2-10 KB of XML; the actual application can be dozens or hundreds of MB of JARs hosted on the application server.
- Most applications list multiple JARs - a main archive and several dependency JARs; you usually need all of them to run the application.
- These methods work only if the application server is still online; if the vendor's server is offline, the JARs are no longer accessible through the JNLP.
Frequently asked questions
Can I run a downloaded JAR directly with Java?
java -jar filename.jar; otherwise you need to identify the entry point from the application documentation.
