How to Update a Minecraft Server Safely

Updated · MCJarHub

Stop the server, back up the world folders and configs, check that your plugins or mods support the new version, install the Java version it needs, replace the server jar, and watch the log on the first start. Worlds upgrade automatically and cannot be downgraded.

Two kinds of update

  • A new build of the same Minecraft version (e.g. a newer Paper 1.21.11 build): low risk, contains fixes. PaperMC recommends updating builds at least weekly.
  • A new Minecraft version (e.g. 1.21.11 → 26.x): upgrades your world permanently, often needs a newer Java, and every plugin or mod must support the new version.

The newest Minecraft release is Minecraft 26.3; see which server software already supports it on that page and on /latest.

Step by step

  1. Stop the server cleanly with stop. Never replace jars while it is running.
  2. Back up the world folders (world, plus world_nether and world_the_end on Bukkit-based servers), the config files and the plugins/ or mods/ and config/ folders. Keep the backup somewhere other than the server folder.
  3. Check compatibility. For a Minecraft version change, confirm every plugin or mod has a release for the new version. Plugin servers: many plugins break on new major versions until updated. Modded: the whole modpack moves together.
  4. Check Java. 1.20.5–1.21.11 need Java 21; 26.x needs Java 25 (see the full table). Install the new Java and point your start script at it — otherwise you get an UnsupportedClassVersionError.
  5. Swap the jar. Download the new server jar (Paper, Vanilla, Fabric…), replace the old file and update the file name in your start script if it changed. Forge/NeoForge: run the new installer with --installServer in the server folder — see the Forge and NeoForge guides.
  6. Update plugins or mods. On Paper you can drop new plugin jars into plugins/update/; they replace the old ones on the next start.
  7. Start and watch the log. The first start on a new Minecraft version upgrades the world, which can take a while. Look for errors from plugins or mods before letting players in.

Things you can't undo

  • No downgrades: once a newer Minecraft version has opened a world, older versions can't load it safely. Going back means restoring the backup and losing everything since.
  • Chunks are upgraded on load: some changes (for example new terrain in already generated areas) only affect chunks as they are loaded or newly generated.

Paper: stable vs experimental builds

When a new Minecraft version comes out, PaperMC first publishes experimental (alpha/beta) builds. MCJarHub marks them on every version page. For a live server, wait until the version has stable builds and your plugins have caught up; use the experimental builds on a copy to test.

Should you update right away?

Only when your plugins or mods are ready. Many servers stay on a long-lived version (1.20.1 for Forge modpacks, 1.21.x for plugin servers) for months. Security fixes are the exception: for 1.7–1.18 servers, apply the Log4Shell mitigation shown on each version page even if you don't update. The new 26.x numbering is explained in Minecraft 26.x version numbers.

FAQ

Can I downgrade a world after updating?
No. Once a newer version has opened a world, older versions cannot load it safely. Restore your backup instead.
How often should I update Paper builds?
PaperMC recommends updating builds regularly (at least weekly) within the same Minecraft version, since builds contain fixes.
Should I update on release day?
Only if your plugins or mods already support the new version. Many admins wait for stable Paper builds and plugin updates.