To update a Minecraft server, stop it, back up the whole server folder, replace server.jar with the new version from Minecraft.net (or a new Paper build), make sure the Java version matches, and start it again. The world upgrades itself on the first start, and every player then updates their game to the same version. The current release is Minecraft 26.3, which needs Java 25. Below are the steps for vanilla, Paper and modpacks, how to change a server to an older version like 1.21.11 or 1.20.1, and fixes for the “incompatible version” errors.
Minecraft server update: why you have to do it
A Java server only accepts players on its own version. When the game updates, players’ launchers move to the new version and they get “Outdated server” when they try to join, while anyone still on an old game sees “Outdated client” on a newer server. So the server and every player have to be on the same version, and updating the server is part of every game update.
Before you update: back up, and check Java
Updating is the moment worlds get lost, so back up first. Stop the server (stop saves the world), then copy the whole server folder somewhere else: the world folders, server.properties, ops.json, the whitelist and ban lists, and your plugins and configs. There’s no supported way back: once a newer version upgrades a world, older versions can’t be relied on to open it, so the backup is your undo button.
Then check Java, because a version jump can need a new one. Moving from 1.21.11 to 26.1 or later is the big one: 26.1 was the first version to require Java 25.
| Minecraft version | Java needed |
|---|---|
| 26.1, 26.2, 26.3 | Java 25 |
| 1.20.5 to 1.21.11 (incl. 1.21.1, 1.21.4, 1.21.10) | Java 21 |
| 1.18 to 1.20.4 (incl. 1.20.1) | Java 17 |
| 1.12 to 1.16.5 | Java 8 |
Run java -version to see what you have. If the new server stops with UnsupportedClassVersionError, Java is too old.
How to update a vanilla Minecraft server
A vanilla update is a file swap. Download the new server.jar, put it where the old one was under the same name, and start the server; it converts the world to the new format as it loads. The whole thing takes a few minutes, plus the time to copy your backup.
- Warn players:
say Updating the server in 5 minutes, thenstop. - Back up the server folder (see above).
- Download the new server jar from the official download page.
- Rename it to the file name your start script uses (for example
server.jar) and replace the old one. - Install the Java version the new release needs, if it changed.
- Start the server and read the console. When it prints
Done, join on the updated game.
Optional: start once with java -jar server.jar --forceUpgrade --nogui to convert every chunk up front instead of as players visit them. It takes longer on big worlds, and it makes the world unusable on older versions, so only do it with a backup in hand.
After the update, check server.properties. Recent versions moved settings around: since 1.21.9, pvp and command blocks are game rules, game rules were renamed in 1.21.11, and 26.3 turns the whitelist on by default. The server properties guide lists what changed.
How to update a Paper server
Paper updates the same way, with one extra step for plugins. PaperMC’s own routine is: back up, update the plugins, then swap the Paper jar while the server is stopped. Never replace jars while the server is running.
- Back up the world folders, server configs, and the plugin jars and plugin configs.
- Create a folder named
updateinsidepluginsand put the new plugin jars there. Paper swaps them in on the next start. - Download the new Paper build, stop the server, rename the new jar to match your start command, and replace the old one.
- Start the server and watch the log for plugin errors. A plugin that hasn’t been updated for the new version is the usual problem.
PaperMC advises against fully automatic updates, because a plugin conflict can slip in unnoticed. If you automate it anyway, keep working backups.
How to update a modded server (Fabric, Forge, NeoForge, modpacks)
A modded server is updated as a set: the loader, every mod and the players’ copies all have to match the new version. Update the loader by running its installer for the new Minecraft version (NeoForge: java -jar neoforge-installer.jar --installServer), then replace each mod with the build for that version and loader. Players need the same mod list, or they’re refused with a mod mismatch.
Modpacks (ATM10 and similar) ship as a server pack per release. Download the new server files for the pack, replace the mods and config folders, keep your world, server.properties and player lists, and read the pack’s changelog for anything that needs a fresh world.
GTNH documents its update process: back up the entire server folder, delete config, libraries, mods (and resources and scripts if present), copy in the same folders from the new server download, redo your config changes by hand rather than copying old config folders over, and restore config/JourneyMapServer from the backup so players keep their maps. The GTNH version must match exactly between the server and every player.
Moving a modded world to a whole new Minecraft version often isn’t possible, because the mods themselves change between versions. Unless the pack says an upgrade is supported, expect a new world when it moves to a new Minecraft version. More on loaders in how to make a modded Minecraft server and the Fabric server setup guide.
Update a Minecraft server in Docker
With the itzg/minecraft-server image, pull the image for the version you want and recreate the container: docker pull itzg/minecraft-server (or a specific tag), then docker compose down and docker compose up -d. The world lives in the mounted data folder, so back that up first.
How to change a Minecraft server version (or go back to an older one)
Changing to another version is the same swap with an older or newer jar. Mojang’s download page only offers the current release; each version’s page on the Minecraft Wiki links that version’s official server jar, and Paper and the mod loaders offer installers per version. Pick the version your mods or players need, such as 1.21.1 for ATM10, or 1.20.1 if your modpack is built for it.
Going back is where people lose worlds. A world that has already been opened on a newer version shouldn’t be loaded on an older one. To downgrade, restore the backup you made before the update, or start a fresh world on the older version.
Minecraft server incompatible version errors after an update
| Error | Cause | Fix |
|---|---|---|
| Outdated server (I’m still on 1.21.11) | The player’s game is newer than the server | Update the server, or the player picks the server’s version in the launcher |
| Outdated client (Please use 26.3) | The server is newer than the player’s game | The player updates their game |
| Incompatible or mismatched mods | Player’s mods differ from the server’s | Give everyone the same pack version |
UnsupportedClassVersionError on start |
Java too old for the new version | Install Java 25 for 26.x, Java 21 for 1.20.5 to 1.21.11 |
| Plugin errors on start | Plugin not updated for the new version | Update or remove it; check the log |
| Friends can’t join after updating to 26.3 | Whitelist now on by default | whitelist add Name |
Want players on newer game versions to join an older server? The ViaVersion plugin (Paper, Fabric, Velocity and others) lets newer Java clients connect to older servers, which buys time while your plugins catch up. More fixes in outdated client and version mismatch.
Bedrock servers
Bedrock Dedicated Server follows the same rule: the server and its players must be on the same version, so update it whenever the game updates, with a backup of the worlds and config files first. Or let Bedrock server hosting keep it current.
FAQ
Does updating a Minecraft server delete the world?
No, the world is upgraded in place. But updates are when worlds break, so make a backup first, and keep it in case you need to go back. See backup and recovery.
How to update a Minecraft server to the latest version?
Download the latest server jar from Minecraft.net (26.3 as of October 2026), stop the server, back up, swap the jar, update Java to 25 if you were on 1.21.x, and start it.
What Java version does a Minecraft server need?
Java 25 for 26.1 and newer, Java 21 for 1.20.5 to 1.21.11, Java 17 for 1.18 to 1.20.4, Java 8 for 1.12 to 1.16.5.
Can I update a modded server to a new Minecraft version?
Only when every mod has a build for the new version and loader. Most modpacks stay on one Minecraft version, so you update the pack within that version instead.
How often should I update?
For vanilla, when a new release is out and your players have updated. PaperMC recommends updating Paper at least weekly within a version for fixes.
Skip the update routine
On GameTeam’s Minecraft server hosting, updating to the latest release is stop, then start: the server updates itself as it boots. To pick a specific version, the version changer swaps Vanilla, Paper, Purpur, Forge, NeoForge or Fabric and the Minecraft version in place, and handles the matching Java image; if a server ever shows UnsupportedClassVersionError, the fix is switching that image, which the copilot can do for you. Or tell the AI copilot “back up the world, then update the server to 26.3 and tell me which plugins don’t support it yet”: it makes the backup, switches the version, checks /plugins and /mods against CurseForge and Modrinth for outdated files, and reads the log after the restart. Click Backup Now any time, and Premium plans take automatic daily backups. Pay per GB of RAM from $0.49/GB a week, unlimited slots. Setting up from scratch? Start with how to make a Minecraft server, or let Minecraft server hosting handle every update from here.
