Minecraft 26.1 on Your Server: What Changes (Version Numbers, World Folders, Java 25 and Plugins)

Why there's no Minecraft 1.22: the new numbering

After 1.21.11 (December 2025) came not 1.22 but 26.1. Since 2026, the first number is the year (26), the second is that year's update and the third, the fixes. So 26.1.1 and 26.1.2 are fixes for 26.1; 26.2 came out in June and 26.3 in September.

For a server it matters in two ways. Your players have to look for “26.1” (or whichever it is) in the launcher, not “1.22”. And scripts or programs that assumed every version starts with “1.” can get it wrong when comparing versions or picking the Java version.

26.1, 26.1.1 and 26.1.2 speak the same language: someone on 26.1.2 can join a 26.1 server without trouble. Between 26.1 and 26.2 they don't: you need the same version or ViaVersion on the server.

Java 25: required since 26.1

The official 26.1 release notes say it plainly: the game needs Java 25. So does the server. If you start it with Java 21, it shuts down immediately with an UnsupportedClassVersionError mentioning “class file version 69.0”: 69 is Java 25.

On your PC, install Java 25 (for example, Temurin, at adoptium.net) and check in a terminal with java -version which one comes up. The Java bundled with the launcher is for the game, not for your server.

The game now reserving 4 GB of RAM and using a different garbage collector (ZGC) is a launcher thing, for the game on your PC. The server's RAM is still decided by whoever starts it.

The full table of which Java each version needs is in the Java guide for the server.

Where is world_nether: the world folders since 26.1

Up to 1.21.11, a Paper (or Spigot) server had three separate folders: world for the surface, world_nether and world_the_end. The regular game, on the other hand, stored the Nether in world/DIM-1 and the End in world/DIM1.

Since 26.1, the game stores each dimension in world/dimensions/minecraft: overworld (the surface), the_nether and the_end, each with its region, entities and poi folders. Paper dropped its usual layout and moved closer to the regular game's, with each world's configuration (paper-world.yml) inside each dimension. Multiverse worlds go there too (how it looks with several worlds).

More things move: player data goes to world/players (data, advancements and stats); in the regular game, world-wide data, such as game rules (game_rules.dat) or weather (weather.dat), goes to world/data/minecraft; and maps go to world/data/minecraft/maps, where map_1.dat is now called 1.dat. Paper, which keeps separate rules and weather for each dimension, stores them inside each one (for example, in world/dimensions/minecraft/overworld/data/minecraft).

What affects you: if you regenerate the Nether, you now delete world/dimensions/minecraft/the_nether; if you have a backup script that copied world_nether, change it; and programs that read the world (editors, map viewers) need to be up to date with 26.1.

world/
├── level.dat
├── data/minecraft/        rules, weather, maps…
├── dimensions/minecraft/
│   ├── overworld/         region, entities, poi
│   ├── the_nether/
│   └── the_end/
└── players/               data, advancements, stats

What happens to your world when you move to 26.1

It's converted automatically the first time it starts with the new version. On Paper you'll see it in the console: a “World storage migration is required during startup” warning and a 30-second wait in case you don't have a backup (“If you do not have a backup: interrupt the server now”). Then it moves the Nether and the End inside world and deletes the old folders.

That first startup takes longer than usual, especially with a big world. Let it finish: interrupting it halfway is the easiest way to break a world.

It's one-way. A world converted to 26.1 doesn't open properly in 1.21.11: it wouldn't even find the dimensions where it expects them. That's why the backup is made before, not after.

Plugins and mods: which ones stop working

Since 26.1, Mojang publishes the server with its internal names visible, and Paper stopped translating the old names. Plugins that dug into the server's guts using Spigot's names (what's called NMS) don't work on 26.1, whether you use Paper or not: Paper announced it in December 2025.

Plugins that only use the Paper or Bukkit API usually keep working. Even so, before upgrading, check each one's page (Hangar, Modrinth or SpigotMC) for a version for 26.1 or later. If the one you can't do without doesn't have one, wait.

With mods it's slower: Fabric, Forge and NeoForge already have 26.x versions, but each mod has to be updated on its own, and many big modpacks are still on 1.20.1 or 1.21.1.

How to move your server to 26.x on NapNodes

New servers are already created on the latest Paper version, with the new folders: there's nothing to convert there. This is for one you have on 1.21.x.

1. Make a backup

   In “Backups”, create one. It's your only way back. (The free server has no backups.)

2. Check your plugins

   In “Mods & plugins” you can see the ones you have. Check that each one has a version for 26.x.

3. Change the version

   “Mods & plugins” → “Server type” tab → Paper → choose the version → “Change”. The panel stops the server, makes another backup if there's room, sets Java 25 and starts it.

4. Watch the “Console”

   You'll see the conversion warning and the 30-second countdown. Wait for “Done” to appear: then you can join.

5. Tell your friends

   They have to join with the same version (in the launcher, “Installations” → “New installation”) or, if anyone is behind, install ViaBackwards (ViaVersion guide).

Should I stay on 1.21.11 or upgrade?

Staying makes sense if an essential plugin or mod doesn't exist for 26.x. 1.21.11 is the last version with Java 21 and the old folders.

Security is the argument for upgrading: according to the Paper API, 1.21.11 lost support on 15 June 2026, and Paper points out that it doesn't backport fixes for exploitable bugs to old versions. And the game's new content (the new baby mobs in 26.1, the sulphur caves in 26.2, the forest in 26.3) only shows up on an up-to-date server.

If you stay, keep the server on 1.21.11 and let people playing on 26.x join with ViaBackwards. What you can't do is downgrade later: the downgrade guide explains why.

Frequently asked questions