Before You Update: Make a Backup
A Minecraft version update is one of the few operations that can permanently alter your world data. Some version upgrades convert chunk formats in ways that cannot be undone. If something goes wrong and you have no backup, you may lose the world entirely. Take a backup before you do anything else.
The safest approach is a full backup: your entire server directory including the world folders, the plugins/ folder and all its configs, and server.properties. If your panel has a built-in backup tool, use it now. If you manage your server manually, download a zip of everything to your local machine. See our server backup guide for how to set up automated backups so this step is always covered before future updates too.
Once the backup is confirmed, stop the server. Do not update a running server.
For Vanilla Servers: Download the New JAR
Go to minecraft.net/en-us/download/server. The page always shows the latest version. Click the download link to get the new server JAR. The file is named something like minecraft_server.1.21.5.jar.
Rename your existing server JAR to something like server-old.jar before replacing it. This preserves your rollback option without deleting anything. Upload the new JAR to your server directory and rename it to match whatever your startup script expects, typically server.jar. Start the server and watch the console for any errors.
For Paper Servers: Download from papermc.io
Paper builds are tied to specific Minecraft versions. You need the Paper build for the new Minecraft version, not just any recent build. Go to papermc.io/downloads/paper, select the new Minecraft version from the dropdown, and download the latest build for that version. The latest build number is always the safest choice -- builds are numbered sequentially and each one fixes issues found in the previous.
Paper's file naming convention includes the version in the filename, such as paper-1.21.5-123.jar. Keep the old Paper JAR in the directory under its original name as a rollback option. Upload the new JAR and update your startup command to point to it. On NetSkyway, the startup command is set in your server's panel settings. On a self-managed server, edit your launch script to reference the new filename.
If you are not already running Paper and want to migrate from vanilla or Spigot, our Paper server setup guide covers the full migration process.
Replacing the Server JAR
The actual swap is simple. Your server directory has one JAR file that the startup command references. You are replacing that file. The worlds, plugins, configs, and all other data stay exactly where they are -- none of it moves. The only thing changing is the server engine JAR.
Steps in order:
- Stop the server completely.
- Rename the old JAR (do not delete it yet).
- Upload the new JAR.
- If your startup command references a fixed filename like
server.jar, rename the new JAR to match. Otherwise update the startup command to reference the new filename. - Start the server and watch the first 60 seconds of console output carefully.
On first start after a version update, the server will convert any existing chunks to the new format. This can take a few minutes if you have a large world. During this process the console will print conversion progress. Wait for it to finish before testing connectivity.
World and Plugin Compatibility Notes
Your existing world carries over to the new version. Minecraft is designed for forward compatibility -- worlds from older versions always load on newer servers. The reverse is not true: a world opened on 1.21 cannot be loaded on 1.20. This is why the backup step matters.
Plugins are a bigger concern. Many plugins release updates for each Minecraft version on the same day or within a few days of a release. Before updating, check each plugin's download page for a version-compatible release. Plugins that have not been updated for the new version may work fine, may crash silently, or may throw errors on startup. The console will tell you which plugins failed to load. For any plugin that breaks, check its Hangar, Modrinth, or SpigotMC page for an updated version, a fork, or an alternative. Running an updated Paper server with a single outdated plugin is generally safe to test, but running with multiple broken plugins can cause cascading errors that are harder to diagnose.
If Something Breaks: How to Roll Back
If the new version causes problems you cannot quickly fix, rolling back is straightforward because you kept both the old JAR and a backup.
- Stop the server immediately. Do not let it run on the new version longer than necessary if you plan to roll back, because any chunks it loads and converts cannot be opened by the old server.
- Delete or archive the new JAR.
- Rename the old JAR back to its original name (or update the startup command).
- Restore your world folders from the backup you made before starting. This step reverts any chunk conversions the new version performed.
- Start the server on the old JAR. Verify everything is working before telling players to reconnect.
If you did not take a backup and the new version converted chunks, you cannot safely downgrade the world data. This is why the backup step is mandatory, not optional.