Short Answer 
To open a JNLP file on Windows 11, first install Java from the official website. Then, locate your JNLP file, right-click on it, and choose “Open with” to select “Java(TM) Web Start Launcher,” ensuring to set it as the default application if desired.
Step 1: Install Java
To begin, ensure that you have Java installed on your Windows 11 computer. Visit the official Java website to download the latest version. Follow the installation prompts to complete the setup. Having Java installed is crucial for running JNLP files, as they require Java Web Start to function properly.
Step 2: Locate Your JNLP File
Once Java is successfully installed, find the JNLP file you want to open. Typically, this file is located in your Downloads folder or the specific directory where you saved it. Make sure you know the file’s location to easily access it during the next steps.
Step 3: Open with Java Web Start Launcher
Now, right-click on the JNLP file to bring up the context menu. Select the “Open with” option and choose “Java(TM) Web Start Launcher.” If it doesn’t appear, select “Choose another app,” navigate to the Java installation directory (usually C:Program FilesJavajre[version]bin), and select javaws.exe. To make this the default for future JNLP files, check the box for “Always use this app,” then click OK.