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Key takeaways
5- Paper 26.3 build 149 was on the beta channel on 4 October 2026; check Paper's downloads page before choosing a build.
- Minecraft 26.3 and Paper 26.3 require Java 25 according to their version data.
- Check your own server.properties file because existing whitelist settings are retained.
- Back up worlds and configuration before upgrading; a 26.3 world cannot be downgraded to an older version.
- Paper plans a config merge for 26.4, but migration details are not published yet.
This update is for owners planning to move a Paper server to Minecraft 26.3, also called Wilderness Bound. You will have a checklist for deciding whether to wait, preparing your server and avoiding a world downgrade you cannot undo.
Check whether Paper 26.3 is ready for your server
Minecraft Java Edition 26.3 was released on 15 September 2026. Paper supports 26.3, but its latest listed build on 4 October is build 149 on the BETA channel. Paper's downloads page still presents 26.2 as the standard download and puts 26.3 builds behind an experimental builds toggle. Treat a 26.3 Paper build as a beta choice, not as the normal stable update.
If your server depends on being available, or a plugin has no confirmed 26.3 support, waiting is a reasonable choice. If you want to evaluate the update, do it on a separate copy first. Paper recommends being present during updates and advises against automatic updates. Read the Paper downloads page and the Paper update guideSource site before replacing a live server jar.
Paper 26.3 includes Minecraft changes such as the /compute and /posteffect commands, and changes to data components and item tags that may affect data packs or plugins. The removed #brewing_fuel item tag no longer works; Minecraft 26.3 uses the minecraft:brewing_fuel data component instead. Check with each plugin or data pack author if your server relies on these areas.
Prepare Java 25 and check the whitelist
Minecraft 26.3 lists Java SE 25 as its minimum Java version, and Paper's 26.3 version data also lists Java 25. Before changing the server jar, make sure the runtime that launches your server uses Java 25. Pterodactyl's yolks repository lists a Java 25 image, but whether your panel offers it depends on the host's egg setup.
Minecraft's server.properties documentation lists white-list as defaulting to true in 26.3. That is a default for new or regenerated settings, not proof that an existing server file changed. Check your own file before opening the server to players. enforce-whitelist still defaults to false.
For Java selection and file checks, use the steps for your server environment:
- Check the Java version available to the account that runs the server. Install or select Java 25 if needed, following your operating system's package or Java installation steps.
- Stop the server before changing its jar or Java runtime. Back up the world folders, server configuration files and plugin jars.
- Open
server.propertiesand check the currentwhite-listvalue. Keep the value your community intends to use.
- Check the File Manager or SFTP for your world folders,
server.properties, and plugin jars, and use the Backups tab to create a backup before updating. - Open the Startup tab and check the Docker image setting for Java 25. If
java_25is not offered, ask your host whether it can be enabled. - Use the File Manager to inspect
server.propertiesand itswhite-listvalue. Stop the server from the Console before replacing files.
- Use the Files / FTP page to make a copy of the world folders, configuration files and plugin jars before updating.
- Check with your host which Java runtime the server uses and whether Java 25 is available. Use the panel's JAR selection for the server jar.
- Inspect
server.propertiesthrough Files / FTP and confirm thewhite-listvalue. Stop the server from the console before replacing its jar.
Back up before upgrading a world
Paper's 26.3 announcement says backups are mandatory and that a world upgraded to 26.3 cannot be downgraded to a lower version. A copied jar is not a world backup. Save the world folders and server configuration files somewhere you can access separately, and make sure you know how to restore them before starting the new version.
Follow the procedure for your environment. Keep the original server stopped while you replace its jar, then check the startup log after restarting. Paper's update guide recommends putting updated plugin jars in the plugins/update folder and restarting so they apply together. Confirm that each plugin supports the target version with its author or official project page; do not assume that a plugin working on 26.2 will work on 26.3.
- Stop the server. Copy the world folders, configuration files and plugin jars to a separate backup location. Follow a backup and restore plan that you have already checked.
- Update plugin jars only after checking their compatibility. Place them in
plugins/updateif using Paper's update method. - Download the intended Paper 26.3 build from Paper's downloads page. Replace the old jar while the server is stopped, naming the new jar to match the startup command.
- Start the server and watch the console log for errors. If you need to return to the previous version, restore the pre-upgrade world backup as well as the old server files. Do not load the upgraded world in an older version.
- Stop the server in the Console. Create a backup in the Backups tab and confirm it covers the world folders and configuration. Download or store a separate copy before proceeding.
- After checking plugin compatibility, use the File Manager or SFTP to place updated plugin jars in
plugins/update. - Use the File Manager to replace the Paper jar while stopped. In the Startup tab, make sure the startup command names the jar you installed. Start the server and watch the Console for errors.
- If recovery is needed, restore the pre-upgrade world and files from the backup. An older jar alone cannot make an upgraded world safe to downgrade.
- Stop the server in the console. Use Files / FTP to copy the world folders and configuration files to a separate location before changing versions.
- Check plugin compatibility, then place updated plugin jars in
plugins/updateif you are using Paper's update method. - Use the panel's JAR selection to choose the intended Paper 26.3 jar. Start the server and watch the console output for errors.
- To recover, restore the pre-upgrade world and files. Do not start that upgraded world using an older server version.
For a fuller version-by-version checklist, see our guide to updating Paper without breaking plugins.
Plan for the 26.4 config merge without guessing
Paper says it is preparing a config merge that will bring almost all options now split across Bukkit, Spigot and Paper config files together. The current plan is for it to land in 26.4.
The tracking issue mentions a small number of renames and removals, but it does not yet publish final file names or a migration procedure. Do not move settings or write a migration script based on guesses. Keep a copy of your current Bukkit, Spigot and Paper config files, and check Paper's announcement and config merge issue for details when they are published.
Paper's update guide also recommends backing up configuration files before an update. Our Paper setup guide covers the initial server files and configuration.
