Minecraft Snapshot 21w43a Server Jar Download

Version facts

What changed

Newest upstream commits:

• #1 · 27 Oct 2021 The edge between old and new world generation is now adjusted when you upgrade a world
• When generating close to old chunks hew terrain is adjusted to better match the existing terrain at the borders
• In old chunks, if there is Bedrock at y=0, the column below will be filled with Deepslate Worlds upgraded in this snapshot will permanently have this deepslate, so if you want new caves under height 0 later, make sure to keep a backup before upgrading
• Worlds upgraded in this snapshot will permanently have this deepslate, so if you want new caves under height 0 later, make sure to keep a backup before upgrading
• The old Bedrock between y=0 and y=4 in old chunks gets replaced with Deepslate

Compatibility

No plugins or mods — the unmodified game exactly as Mojang ships it (data packs still work).

Players need a Minecraft: Java Edition Snapshot 21w43a client on the same version.

Minecraft Snapshot 21w43a in other server software

Known issues & safety notes

• Preview builds are experimental: they can corrupt or irreversibly upgrade worlds, and most plugins and mods do not support them yet. Test on a copy of your world.

How to set up Minecraft Snapshot 21w43a

1. Install Java 16 or newer (e.g. Eclipse Temurin) and check it with java -version.
2. Download server.jar from Mojang (button above) into an empty folder.
3. Start it once with the script below; it creates eula.txt and stops.
4. Set eula=true in eula.txt to accept the Minecraft EULA, then start again. Players join on port 25565.

#!/bin/sh
# start.sh — Minecraft 21w43a
cd "$(dirname "$0")"
JAVA_MAJOR=$(java -version 2>&1 | awk -F'"' '/version/ {split($2, v, "."); print (v[1] == "1") ? v[2] : v[1]}')
if [ "$JAVA_MAJOR" -lt 16 ] 2>/dev/null; then
  echo "Java 16 or newer is required (found Java $JAVA_MAJOR)."
  exit 1
fi
java -Xms4G -Xmx4G -jar server.jar nogui

@echo off
REM start.bat — Minecraft 21w43a
REM Needs Java 16 or newer: run "java -version" to check.
java -Xms4G -Xmx4G -jar server.jar nogui
pause

Rule of thumb: 2–4 GB for a few friends, 6–10 GB for a public server with plugins. Set -Xms equal to -Xmx and leave 1–1.5 GB for the operating system. How much RAM?

Docker

docker run -d -p 25565:25565 -e EULA=TRUE -e TYPE=VANILLA -e VERSION=21w43a --name mc itzg/minecraft-server

Uses the community itzg/minecraft-server image, which downloads the file itself.

Upgrading

• Newer: Minecraft Snapshot 21w44a
• Previous: Minecraft Snapshot 21w42a
• How to update a Minecraft server safely