Minecraft 26.3 Server Update: Whitelist, Java 25 and Paper

Minecraft 26.3, the Wilderness Bound drop, came out on September 15, 2026. Players got the dappled forest, poplar wood, abandoned camps, cushions and straw beds, and our Wilderness Bound post walks through all of it. This post is for whoever runs the server.

Three things matter for you: a new default in server.properties that keeps players out of fresh servers, the Java version, and whether the software your server depends on is ready. We checked every project below on October 1, 2026, and the sources are linked. Beta labels change quickly, so every status comes with a date.

The short version

1. A new 26.3 server starts with the whitelist on. Add players with whitelist add <name> or run whitelist off. A server you update from 26.2 keeps the setting it had.
2. 26.3 needs Java 25, just like 26.1 and 26.2. If you come from 1.21.x, Java changes too.
3. Paper 26.3 and NeoForge 26.3 are still in beta. Fabric has a stable loader and Fabric API releases for 26.3.
4. Geyser supports Java 26.2, not 26.3. Crossplay servers should wait.
5. Back up before you update. A world that has been upgraded to 26.3 cannot go back to 26.2.

New servers start with the whitelist on

Under Server Properties, Mojang's 26.3 changelog has a single line: "The white-list property is now true by default."

A default only matters when the server creates server.properties from scratch. If you update an existing 26.2 server, its server.properties already has a white-list= line, and that value stays. The servers that get caught are brand new ones, and servers where someone deleted server.properties to start clean.

On those servers, anyone who is not on the list is disconnected. A vanilla server shows "You are not white-listed on this server!". Paper, Spigot and Purpur take the text from spigot.yml instead, and the default there is "You are not whitelisted on this server!" (PaperMC docs). Operators still get in, because ops are automatically whitelisted, as the Minecraft Wiki notes. So if you made yourself op first, you can join while your friends cannot. That looks like a connection problem. It is a setting.

To let your friends in, add them from the console:

whitelist add Steve
whitelist add Alex
whitelist list

In the console you type commands without a slash. In game, as an operator, it is /whitelist add Steve. The player does not need to be online.

To open the server to everyone, run whitelist off. The server writes that to server.properties itself, so it stays off after a restart. Setting white-list=false in the file and restarting does the same. On Space-Node you do both from the panel: commands in the live console, and server.properties in the file manager.

For a server that is only for friends, the new default is the sensible one. Leave it on and add the people who play.

Java 25, and what changes if you come from 1.21.x

Mojang publishes a small version file for every release, and it names the Java version the game needs. For 26.3 that is Java 25. It was the same for 26.1 and 26.2. The last version on Java 21 was 1.21.11. Paper lists Java 25 as the minimum for its 26.3 builds as well.

If your server runs 26.1 or 26.2 today, Java stays as it is. If it runs 1.21.x, switch to Java 25 before the first start on 26.3. On an older Java the server stops straight away. Paper prints this:

Minecraft 26.1 and newer requires running the server with Java 25 or above.

A vanilla server stops with an UnsupportedClassVersionError that mentions class file version 69.0, which is the Java 25 class format.

In the Space-Node panel you pick the Java version in the Startup tab. If Java 25 is not in the list for your server, ask us in live chat before you update.

Coming from 1.21.x on Paper, two more things change. Since 26.1, Paper keeps the Nether and the End inside world/dimensions/ instead of separate world_nether and world_the_end folders (PaperMC 26.1 notes), so backup scripts and tools that use the old folder names need new paths. And if you copied ZGC flags from a Java 21 setup, drop -XX:+ZGenerational, which is obsolete on Java 25. Our ZGC vs G1GC guide has flag sets for both Java versions.

Removed log lines

The changelog also says "some log lines that server software might look out for have been removed" and points to the Minecraft Server Management Protocol instead. Mojang does not say which lines.

The line panels watch to see that a server has finished starting, the one that ends in For help, type "help", is still in the 26.3 server jar. If you run something else that reads the console, such as a bot that tails the log for joins and leaves or a script that reacts to certain messages, test it after the update.

Smaller changes from the changelog

• Mobs that do not despawn now stop their random walking and swimming when no player is near, the same way other mobs already did.
• Mojang lists better chunk generation performance and faster structure locating. It also fixed a bug where locating a structure created an empty region file for every candidate chunk in terrain that had not been generated yet (MC-311323).
• level.dat now keeps a version_history list with the world's earlier data versions.
• The data pack version is now 121.0, so data packs made for 26.2 may need an update. One example from the changelog: signs no longer run click events in custom text by themselves.
• PaperMC writes in its 26.3 post that it plans to merge almost all Bukkit, Spigot and Paper config options in 26.4. Nothing changes in 26.3, but expect some config work on the next update.

Where the server software stood on October 1

Beta is not a label to ignore. Paper keeps its 26.3 builds behind an "experimental builds" switch on its download page, with the warning "Proceed with caution!". NeoForge explains its -beta suffix as a sign "that breaking changes are still allowed" (NeoForge 26.1 notes). Purpur is built on Paper, so it follows Paper's status.

The last two drops show the pace. Paper's first stable build came 38 days after 26.1 and 40 days after 26.2, after beta phases of 5 and 14 days. NeoForge dropped the beta tag 10 weeks after 26.1 and about 8 weeks after 26.2. That is no promise for 26.3, but it tells you to think in weeks, not days. Paper 26.3 entered beta on September 28.

Crossplay servers: check Geyser first

Geyser's supported versions page lists Bedrock 26.30 to 26.52 and Java 26.2. Bedrock players already have the new drop (Bedrock 26.50), because Bedrock updates itself on every platform, and Geyser supports it. The Java side is the problem. Geyser imitates a 26.2 Java client, so a server only accepts Geyser if it accepts 26.2 clients. The Geyser update for Java 26.3 is open as pull request #6712 and was not released on October 1.

That leaves three choices:

• Stay on 26.2 until Geyser lists Java 26.3. Bedrock players keep joining as before.
• On Paper, add ViaVersion and ViaBackwards 5.12.0. ViaBackwards added 26.3 server support, so the server accepts 26.2 clients, Geyser included. Try this on a copy first.
• On Fabric or NeoForge, wait. Geyser-Fabric and Geyser-NeoForge only run on the Java version Geyser supports, which is 26.2.

If you run a Bedrock Dedicated Server instead of Geyser, update it to the current build, 1.26.52.3 on October 1, so players on the newest Bedrock version can connect. Our Geyser and Floodgate guide covers the crossplay setup itself.

Plugins and mods

A stable server jar does not mean your plugins are ready. This is what the download pages listed on October 1:

Sources: the version lists on Modrinth, and the GitHub releases of CoreProtect and EssentialsX. WorldGuard's install page lists WorldEdit as a requirement.

A plugin that does not list 26.3 may still load. Plenty do. Others load and then fail the first time they meet a new block or item. A test copy shows you which kind you have. A live server full of players is the wrong place to find out.

Cushions need their own check. They are entities, not blocks: Mojang's changelog calls them "Cushion entities", and Paper 26.3 added new events for breaking them. If you rely on a claim or protection plugin, check that its changelog covers cushions before you open the server again.

Modded servers follow a simpler rule: run the version your mods or your modpack target. All The Mods 10 runs on 1.21.1, and the ATM11 beta (0.9.0, September 19) targets 26.1.2, not 26.3. Moving a modpack server to 26.3 is the pack author's call. When a new pack version does come out, our modpack update guide shows how to update without losing the world.

How to update safely

1. Decide whether you need 26.3 now. A crossplay server, a modded server, or one that leans on a plugin without a 26.3 release, such as CoreProtect, can stay on 26.2 for a while. Players who already updated their game can still join a 26.2 Paper server through ViaVersion 5.12.0, which added 26.3 clients.
2. Make a backup in the panel. Also download the world over SFTP, so one copy lives off the server. PaperMC calls backups "absolutely mandatory" for this update, because a world upgraded to 26.3 cannot be downgraded.
3. Test on a copy first, on a second server or on your own PC, and copy the world folder as well. A world upgraded to 26.3 cannot go back to 26.2, so the upgrade itself is what your test has to cover. Our test server guide explains how to set one up.
4. If you come from 1.21.x, set Java 25 in the Startup tab.
5. Set the server to 26.3 in the panel and start it. If the version or build you want is not offered yet, ask us in live chat.
6. Watch the console for the first minute. Missing dependencies, plugins that refuse to load and Java errors all show up there.
7. Open server.properties and check white-list. On an updated server it should still have its old value.
8. Join with two accounts, yours and a friend's. Check inventories, claims, ranks and a trip through a Nether portal.
9. Keep the pre-update backup until the server has run for a week or so with real players.

FAQ

Why can nobody join my new 26.3 server?

New 26.3 servers start with white-list=true in server.properties. Players who are not on the list are disconnected with "You are not white-listed on this server!", or "You are not whitelisted on this server!" on Paper, Spigot and Purpur. Add them with whitelist add <name> in the console, or run whitelist off to open the server.

Does Minecraft 26.3 need Java 25?

Yes. Mojang's version file for 26.3 names Java 25, as it did for 26.1 and 26.2, and Paper lists Java 25 as the minimum for its 26.3 builds. 1.21.11 was the last version on Java 21.

Is Paper 26.3 stable?

Not on October 1, 2026. Paper 26.3 has been on the beta channel since build 134 on September 28, and Paper's download page still offers 26.2 as its main version.

Can I go back to 26.2 after updating?

Not with the same world. PaperMC writes that you cannot downgrade a world after upgrading it to 26.3. Restore the backup you made before the update instead.

Can players on 26.3 join a 26.2 server?

On Paper, yes, if the server runs ViaVersion 5.12.0 or newer, which added support for 26.3 clients. Without ViaVersion, the client and the server need the same version.

Does Geyser work with Minecraft 26.3?

Not directly on October 1. Geyser supports Java 26.2. Keep a crossplay server on 26.2 for now, or on Paper let Geyser connect through ViaBackwards 5.12.0 and test that on a copy first.

Related guides

• Minecraft 26.3 Wilderness Bound: everything the drop adds
• How to whitelist a Minecraft server
• Geyser and Floodgate crossplay setup
• Minecraft Live September 2026: what comes after 26.3

Running a server on 26.3? See the Minecraft plans: Java and Bedrock, NVMe storage, DDoS protection and 9 regions to choose from.