How to Fix “Unable to Access Jarfile” on a Minecraft Server

Direct answer

Your startup command is pointing to a JAR that Java cannot open at that path. Make the filename in the command exactly match the actual server JAR and run the script from the intended server directory.

List the files instead of guessing

Windows:

dir

Linux/macOS:

ls -la

Then copy the real filename into the startup command. Linux filenames are case-sensitive, so Server.jar and server.jar are different.

Example Paper command

java -Xms2G -Xmx2G -jar paper.jar --nogui

If your downloaded file has a build/version in its name, either use that exact name or deliberately rename the file and update the script.

Windows hidden extensions can mislead you

If File Explorer hides known extensions, a file that looks like server.jar may actually be named differently. Paper’s troubleshooting documentation specifically calls out hidden extensions as a common reason the startup script does not match the JAR.

Forge/NeoForge installer warning

Do not rename an installer JAR and try to run it as the server. Modern mod loaders often generate run.bat/run.sh and additional library files; use the loader’s documented server installation procedure.

Official references

These references were checked while preparing this fix. Version-specific behavior can change, so use the project documentation for your exact release when a detail differs.

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