How to update your Minecraft server to 26.x: Java 25, backups and plugins

Since 2026, Minecraft Java Edition is no longer numbered 1.22 but 26.1, 26.2, 26.3 and so on, and the new numbering comes with a more practical change: Java 25 is now required. Updating your Minecraft server to 26.x is therefore more than swapping a .jar file. This guide gives you a complete migration checklist, from backups to a rollback plan, for Vanilla, Paper, Spigot and Purpur.

What changes with the 26.x numbering

The last release of the old series is 1.21.11, released in December 2025. Since then, Mojang numbers Java Edition releases as YY.D.H: the year, the number of the content drop within that year, then an optional hotfix.

• 26.1 (March 2026), followed by hotfixes 26.1.1 and 26.1.2;
• 26.2 (June 2026);
• 26.3 (September 15, 2026), the current stable release as of mid-October 2026;
• 26.4, in snapshots at the time of writing.

Key takeaway: 26.1 is the direct successor of 1.21.11. A 1.21.x server moving to 26.3 skips three content drops at once, with as many world conversions.

Which Java version for which Minecraft version?

This is the number one reason servers refuse to start after an update. The table below lists the Java versions recommended by the Paper documentation, which also apply to Vanilla, Spigot and Purpur.

Good news: Java 25 also runs older versions. You can install Java 25 before the update, check that your 1.21 server still starts, then change the Minecraft version afterwards. The reverse does not work: a 26.x server started with Java 21 stops immediately with an error like this one:

java.lang.UnsupportedClassVersionError: net/minecraft/bundler/Main has been compiled
by a more recent version of the Java Runtime (class file version 69.0),
this version of the Java Runtime only recognizes class file versions up to 65.0

Class file version 69 means Java 25, version 65 means Java 21. If you see this message, the problem is neither your world nor your plugins: it is only the Java version.

Check and switch your Java version

On a Linux server you manage yourself, start by checking which version is in use:

java -version
# If several versions are installed (Debian / Ubuntu)
update-alternatives --config java

If Java 25 is not installed yet, use your distribution's package or a well-known OpenJDK build (Eclipse Temurin, for example). The safest option is to call the binary by its full path in your start script, so you do not depend on the system default:

/usr/lib/jvm/java-25/bin/java -Xms4G -Xmx4G -jar server.jar --nogui

The exact path depends on your setup. On a hosting panel, the Java version is usually picked in the server's startup settings (Java image or runtime): select Java 25 before starting the new version.

Where do Paper, Spigot and Purpur stand?

As of mid-October 2026, here is the status of the main server software:

• Paper ships 26.3 builds on its stable channel. The 26.1.x and 26.2 branches can still be downloaded, but only the latest version gets fixes: aim for 26.3.
• Purpur, which is based on Paper, also publishes 26.3 builds.
• Spigot is still built with BuildTools. With Java 25 installed: java -jar BuildTools.jar --rev 26.3.
• Modded servers: mod loaders and especially modpacks follow their own schedule. Only update once the modpack officially releases a server version for your target 26.x release.

An often forgotten point: if you run a proxy in front of several servers, it must also support your players' version, and its own release may require Java 25. Check its documentation before touching the servers behind it.

The complete pre-update checklist

Most guides stop at "make a backup". Here is the list we recommend following step by step.

1. Record the current state: exact Minecraft version, server software build, Java version, and the list of plugins with their versions. A screenshot of the plugins folder and the output of /version is enough.
2. Check every plugin: for each one, look on its download page for a version compatible with your target 26.x release. Sort them into three groups: compatible, waiting for an update, abandoned. For an abandoned plugin, find a replacement before migrating.
3. Identify critical plugins: permissions, economy, region protection, authentication. If one of them is not ready, postpone the update: a server without protection or permissions is worse than a server one version behind.
4. Warn your players: date, expected downtime and the Minecraft version to use afterwards.
5. Stop the server cleanly with the stop command, never by killing the process, so that regions are properly written to disk.
6. Make a full backup: world folders, but also plugins (with their configs and databases), server.properties, the server software's config files, player lists and the old .jar.
7. Test the restore: a backup that has never been restored is only an assumption. Extract it somewhere else and check that it is complete.
8. Set up a test server if you can: a copy of your server on which you run the update first.

Backup example on Linux

cd /opt/minecraft
# The server must be stopped before copying
tar -czf ../backup-before-26x-$(date +%F).tar.gz .
# Check that the archive is readable
tar -tzf ../backup-before-26x-$(date +%F).tar.gz > /dev/null && echo "Archive OK"

Keep a copy of this archive outside the server machine. If the disk fails during the migration, a backup stored in the same place will not save you.

The update, step by step

1. Update plugins first. On Paper and its forks, drop the new versions into the plugins/update folder: they replace the old ones on the next start.
2. Switch to Java 25, as explained above.
3. Replace the server .jar with the 26.x build of your software (Vanilla, Paper, Spigot or Purpur) and update the file name in your start script if needed.
4. Start the server and read the console to the end. Note any plugin that fails to load and any startup error.
5. Test in game with an admin account: login, permissions, main commands, region protection, economy, and a quick tour of the important areas of the map.
6. Reopen to players only once these checks are done.

Should you convert the whole world at once?

By default, chunks are converted to the new format as they are loaded. The Vanilla server (and Paper) also accepts the --forceUpgrade option, which converts the whole world at startup. It takes longer and uses more resources, but avoids lag spikes when players explore old areas. On a large map, run it on your test server first to measure how long it takes.

java -Xms4G -Xmx4G -jar paper-26.3.jar --forceUpgrade --nogui

Most common errors after updating

The rollback plan

This is the part almost no guide covers in detail, yet it is the most important one: a world converted to 26.x cannot go back to 1.21. Putting the old .jar back on a converted world can corrupt chunks or make blocks and items disappear. The only real rollback is restoring your backup.

1. Set a decision rule before you start: for example, "if a critical plugin still does not work after one hour, we roll back".
2. Stop the server with stop.
3. Set the failed state aside (rename the folder instead of deleting it): it will help you understand what went wrong.
4. Restore the full backup: worlds, plugins, configs and the old .jar.
5. Go back to Java 21 if you prefer, although Java 25 also runs 1.21.
6. Tell your players that progress made since the update is lost.

That last point is why you should decide quickly: the longer you wait, the more progress players lose if you roll back. This is also where a test server pays off, since it lets you find problems before they affect the live game.

Plan your server resources

Converting a large world and running a test copy alongside it require headroom in memory and disk space. For example, the OuiBox plans offered on MineServ range from 8 GB of RAM, 4 cores and 50 GB of NVMe storage (€9.98 per month) to 16 GB of RAM, 6 cores and 120 GB NVMe (€21.59 per month), enough to keep backups and a test copy next to your main server.

FAQ

Why is there no Minecraft 1.22?

Mojang dropped the "1." prefix in 2026. The release that could have been called 1.22 is 26.1, followed by 26.2 and then 26.3.

Can I stay on 1.21.11?

Yes, your server will keep working, but players will have to launch the game in 1.21.11 (or you will need a version compatibility plugin), and you will not get new features or fixes.

Does Java 25 break my old plugins?

Rarely. Most plugins compiled for Java 21 run fine on Java 25. What breaks things is mostly the move to Minecraft 26.x, not the Java version itself.

How long does the update take?

For a small server with a few plugins, plan about thirty minutes, backup included. For a large map that you fully convert, the conversion alone can take much longer: measure it on your test copy.