JNLP or Java Network Launch Protocol is a file format that consists of many information like a remote address for downloading your java program and several other applications. These files are mainly used for managing or opening Java apps over a particular network. It is usually available in XML file format. If you want to launch and edit the respective JNLP file on your system’s screen, you just need a text editor with the XML file format. Your PC must have the Java Runtime Environment installed for this task.

While JNLP files are the vital part of Java Web Start technology, it comes in a bundled format with Java Runtime Environment to launch the JNLP files.

Many users reported that JNLP files fail to open on a device while trying to access the same using several attempts. It might have possible that JNLP files fail to detect the necessary software required executing the respective file. Here, we will teach you how to fix JNLP files’ problem fails to open errors.

Opening JNLP Files Right on Your Windows 10

If you want to open JNLP files on your device running on Windows 10, then follow these straightforward steps:

Get started by downloading and installing Java Runtime Environment on your device.
Execute the installer and then pursue on-display directions to install the respective program files.
Perform a right-click on your JNLP file that fails to open.
Then, choose the option “Open With.”
After that, go to the window “How you want to open this File.”
Scroll down and then hit the option “Look for another app on this PC.”
Once the File Explorer window launches, visit the under-offered path:
“C:/Program Files/Java/jre/1.8.0_261/bin”

Now, choose javaws.exe and then press the Open tab. It will launch the JNLP files as required.
Ensure to check the JNLP file opening option that says, “Always use this app to launch .jnlp files.” This option is available in the window that says “How do you want to open this file window” to save JRE as your default app to launch the same.
In case the JNLP file still fails to open, proceed with the command line instructions using the next method.

Running JNLP File on Windows Command Line

If you want to run JNLP files via Command Prompt, then follow these steps carefully:

Choose a particular link on the specific webpage that refers to the .jnlp file. If the browser doesn’t have the appropriate association to execute the Web Start apps, choose the command option “install-dir\jre\javas\bin.” It will be available in the Save/Open window to begin your web start apps.
After that, go to the command prompt and then enter the following path:
“Javaws .”

Note: is the location of .jnlp file in the above-mentioned path.

Opening JNLP Files Automatically

Follow these steps if you want to open JNLP files automatically:

At the start, tap the Window and R keys simultaneously on the keyboard to open the Run box.
Then, enter Settings to reach the Settings page.
Hit the Apps option there.
Go to the left-hand side section and then press the Default Apps tab.
Scroll down and then hit the Choose default apps by file type.
Scroll down and reach the .jnlp file type, followed by tapping the option “Choose a default option.”
Choose the Java Web launcher option.
Now, exit from the Settings page and then launch the File Explorer option.
Next, look and double-tap the JNLP files to check if it is smoothly opening automatically or not?
Windows system needs JRE files to execute for opening JNLP files. In case the file is related to other applications, it may create hindrances in opening the same. To launch the respective file, you can use any supportive methods like opening the file using the Command window, using the automatic file opening method, etc.

Source: https://maxxadvisor.com/how-to-fix-jnlp-file-not-opening-errors/