How to Fix Windows Failed to Launch Lunar Client Error
Are you getting the error message “Failed to Launch Lunar Client: Java launch failed” when launching Lunar Client for Minecraft? The main reasons for this error are a missing or corrupted Java Runtime Environment (JRE) or insufficient RAM allocation in the Lunar Client settings.
Other possible causes include backed up cache folders, interference from other gaming clients, or your antivirus software blocking the client’s processing. This article will discuss different fixes you can apply to resolve the issue and successfully launch Lunar Client.
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1. Perform some preliminary checks
First, perform the following preliminary checks:
- Close and restart Lunar Client.
- Close other applications running in parallel with Lunar Client so that they do not interfere with it.
- Make sure your device is connected to the Internet and that the network connection is stable.
If the above checks do not resolve the issue, apply the remaining fixes.
2. Run Lunar Client as an administrator
You may encounter the error we are discussing if Lunar Client cannot access certain system files. To ensure that restricted access does not cause problems, run the client as an administrator. Doing so will allow Lunar Client to access files or resources that it would not otherwise be able to access.
Follow these steps to run Lunar Client as an administrator:
- Navigate to the folder where Lunar Client is installed.
- Find the executable file for launching the client.
- Right-click the Lunar Client EXE file and select Run as administrator from the context menu.
If launching Lunar Client as an administrator solves the problem, it indicates that an operating system limitation caused this error. Therefore, you should configure the application to always run as an administrator.
3. Delete Lunar Client’s cache folders
Like most game launchers, Lunar Client caches some game data in its cache folders. This helps the client get the required information from these locations faster, which ultimately improves the performance of the client.
However, sometimes the accumulated cache can interfere with client processing, causing unexpected problems. To ensure that cache interference does not cause the error discussed, you should clear all cache folders. Follow these steps to do this:
- Navigate to the following location:
C:\Users\<username>\AppData\Roaming
- Find the lunarclient folder and open it.
- Here, you must delete three folders: Cache Cache, Code Cache, and GPUCache.
- Select the folders, right-click them, and then click Delete.
Run Lunar Client again after deleting the cache folder. If you get the same error again, proceed to the next step.
4. Change the allocated memory in the Lunar Client settings
Lunar Client gives users the freedom to choose how much memory the client should have access to. It helps users manage their system resources efficiently and reduces the burden on their hardware.
While it is a blessing to have this flexibility, don’t be stingy when allocating memory. If you allocate too little memory in the client’s settings to meet the client’s needs, you will most likely encounter the error we are discussing.
To change the memory allocation for Lunar Client, follow these steps:
- Launch Lunar Client.
- Click Settings on the top menu.
- To change memory allocation, drag the slider to Allocated memory.
How much memory you should allocate depends entirely on the amount of memory on your computer. If you have 16GB of RAM installed, allocating 5GB would be a better decision. If the overall memory is less than that, you can allocate it accordingly.
5. Delete the old renderer log file
In addition to stating that Java startup failed, the error message also states that the report could not be submitted. Lunar Client may be unable to submit error reports due to an issue with the old renderer log file, which contains data about previously reported errors and game settings.
Some Reddit users say that deleting this file fixes the issue being discussed. Therefore, if no fixes solve the problem, you should delete the renderer.old file in the Logs folder. Follow these steps to do this:
- Launch the Lunar client.
- Go to About About from the top menu.
- Click Logs Logs under the Folders Folder. Clicking this button will take you to the Logs folder.
- Right-click on the Renderer.old file and click on the DeleteDelete icon.
6. Whitelist Lunar Client in Windows Defender and your antivirus software
Lunar Client is a third-party software application. Therefore, Windows Defender and other antivirus programs installed on your device may interfere with the client’s processing. To prevent this, it is necessary to whitelist the lunar client from your security software.
Our guide on how to allow apps through Windows Defender describes the steps to whitelist apps from the Windows built-in security suite. If you use a third-party antivirus software as an extra layer of protection, you can find instructions for whitelisting the application on its official website.
7. Reinstall Java Runtime Environment
Lunar Client requires Java Runtime Environment to run properly. If it is not installed correctly, some files are corrupted, or one of the files is missing, you may encounter Java-related errors such as the one discussed in this article. To make sure this is not the case, you should reinstall it.
Because newer versions automatically update and repair lost or corrupted files, you don’t need to delete the older version before reinstalling. Follow these steps to install it:
- Go to the Java website.
- Click Download Java下載Java.
- Click Download Java下載Java I’ll repeat it on the next page.
- Once the file is downloaded, run it and click YesYes in the UAC window.
- Then click the InstallInstall button.
If you encounter any problems during the installation, uninstall the existing installation. To do this, open the Setting application and go to the Apps tab on the left. Then, find the Java package from the list of installed programs, click the three horizontal dots next to it, and then click Uninstall.
If the installation window automatically detects an old Java version, click Uninstall to uninstall it.
Play Minecraft smoothly again on Windows
Starting Lunar Client and encountering unexpected errors can be frustrating. Hopefully the above fixes will help you pinpoint the root cause of the “Cannot launch Lunar Client: Java startup failed” error and resolve it. If none of the fixes resolve the issue, you may have to uninstall Lunar Client and reinstall it.
