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Fix “Unable to access jarfile” in a Minecraft startup

Applies to: Java -jar startup of a managed Minecraft service; applies before Minecraft loads, with panel/template-specific paths.
Documentation checked .

Unable to access jarfile is a Java launcher error. Java could not open the JAR named by the launch command, so Minecraft may not have begun loading at all. Adding RAM, resetting a world or updating plugins will not repair an incorrect launcher path. Begin with the filename printed after the error.

Compare the requested file with the actual upload

Read the panel console from the start of the failed attempt and record the exact requested filename. Then open the server's file manager and locate the intended Minecraft server JAR. Compare spelling, capitalization and extension. Linux distinguishes uppercase and lowercase names, and a local desktop can hide an extra extension such as .jar.jar.

Confirm that you uploaded the actual binary download. A ZIP containing several files, a project source archive or an HTML download-error page is not the intended server JAR. Check the official download source and expected file size where provided. Renaming a different file type to end in .jar does not convert it into an executable server.

Check the working directory and launcher field

The startup command's relative JAR path is resolved from its working directory. A JAR uploaded into a nested folder may not match a command expecting it in the main server directory. Inspect the startup JAR-name field if the panel exposes one. Do not assume that changing the visible server name also changes this launch field.

Take a private copy of the current startup information and preserve the existing server files. For a host-managed template, ask support to identify the supported JAR field rather than replacing the entire launch command. The field should name the intended server binary, not a plugin from the plugins directory or an installer that belongs to another server type.

Correct one mismatch

Keep the server stopped while changing launcher files. Either set the supported JAR field to the correct existing filename or upload the verified server binary under the filename the template expects. Choose one approach and record it. Avoid retaining several ambiguously named active binaries while trying different values without notes.

If the file is already in the correct place with the correct name, check the panel upload result and whether the file is readable through the available file tools. Ownership or permission problems may require hosting support. Do not apply broad recursive permissions or make everything globally writable to address a launcher error.

Verify and recover

Start once and check that the launcher proceeds beyond the original error. Confirm the Minecraft/Paper version reported is the version you intended. A replacement JAR that starts successfully can still be the wrong release; do not allow an accidental newer release to upgrade your world unnoticed.

If another error appears, preserve it separately. A class-version or invalid-JAR error means you reached a different stage, not that the same missing-path problem persists. If necessary, restore the previous verified JAR and startup field. Keep world, plugin and configuration folders unchanged. When contacting support, provide the requested path, actual filename, upload source and redacted startup excerpt, rather than a full private configuration archive.

Official references

Paper troubleshooting for an inaccessible server JAR. Paper server downloads and launch command.

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