How do I make a start.bat file for a Minecraft server?

Put the server jar in a folder of its own, generate the script with Windows selected, and save it in that same folder as start.bat. Double-click it to start the server. The first run creates eula.txt and stops: open that file, change eula=false to eula=true, save it and run start.bat again.

Should I use Aikar's flags?

Not by default. As of October 2026, Paper's advice is to try no extra flags first if you run Java 17, 21 or newer, because modern Java handles garbage collection well on its own. Paper suggests Aikar's flags if you have garbage collection problems, or if you run an older Minecraft version or an older Java.

How much memory should I put in -Xmx?

Less than the machine has. Java uses memory on top of the -Xmx value and the operating system needs some too, so Paper's documentation recommends setting it about 1000 to 1500 MB below the memory you have available: with 8 GB free, use about 6.5 GB. To work out how much your server needs in the first place, use the RAM calculator.

It stops the server from opening its own graphical window, so everything happens in the console window the script runs in. The current spelling is --nogui, and the vanilla server still accepts the older nogui. Leave it out if you want that graphical window.

Which Java version does a Minecraft server need?

As of October 2026: Minecraft 26.1 and newer need Java 25, 1.20.5 to 1.21.11 need Java 21, 1.18 to 1.20.4 need Java 17, 1.17 and 1.17.1 need Java 16, and 1.12 to 1.16.5 need Java 8. Type java -version in a terminal to see which one you have.

Why does my server not start when I run the script?

Read the error in the window. 'java' is not recognized as an internal or external command means Java is not installed or not on your PATH. Error: Unable to access jarfile means the jar name in the script does not match the file in the folder exactly. A line about the EULA means you still have to set eula=true in eula.txt. A message that there is insufficient memory for the Java Runtime Environment means you asked for more memory than the machine can give.

Do I need a start script on a hosted server?

Usually not. On a managed host the startup command is normally set for you, and any part of it you are allowed to change lives in the control panel. This tool is for a server you run on your own computer or on a machine you manage yourself.

Minecraft Server Start Script Generator

How to use your Minecraft server start script

A start script is a small text file that holds the command that launches your server, so you start it with a double-click instead of typing the command every time. It belongs in the same folder as the server jar.

On Windows

Choose Windows above and download the file. Or copy the text into Notepad and save it as start.bat with "Save as type" set to "All files", so it does not become start.bat.txt.
Put start.bat in the folder that holds your server jar.
Double-click it. The first run creates eula.txt and stops. Open that file, change eula=false to eula=true, save it and run the script again.

The script ends with pause, so the window stays open after the server stops and you can read any error.

On Linux or macOS

Choose Linux or macOS and save the script as start.sh in the server folder.
Open a terminal in that folder and make the script executable once with chmod +x start.sh.
Start the server with ./start.sh, then accept the EULA the same way as on Windows.

Both scripts switch to their own folder first, so the server finds its world and settings wherever you launch it from.

What the options mean

Memory

The number becomes both -Xms, the memory Java starts with, and -Xmx, the most it may use. Whole numbers are written as 4G. A value such as 2.5 is written in megabytes as 2560M, because Java rejects a decimal point there.

Do not give the server all the RAM in the machine. Java needs memory on top of that number and so does the operating system: Paper's documentation recommends staying about 1000 to 1500 MB below what you have available. The Minecraft server RAM calculator helps you pick the number.

Plain or Aikar's flags

Plain means no tuning flags at all. As of October 2026, Paper's advice is to try that first on Java 17, 21 or newer, and to try Aikar's flags if you have garbage collection problems or run an older Minecraft or Java version. The flags tune Java's G1 garbage collector for the way Minecraft uses memory, and this tool writes them exactly as Paper publishes them. Paper recommends at least 6 to 10 GB of memory with them, or as much as you can spare.

More than 12 GB

Aikar's original post changes five values when the server has more than 12 GB: G1NewSizePercent=40, G1MaxNewSizePercent=50, G1HeapRegionSize=16M, G1ReservePercent=15 and InitiatingHeapOccupancyPercent=20. As of October 2026 Paper's page no longer lists this adjustment, so the tool applies it only when you tick the box. Aikar's own warning applies: if you see more old generation collections afterwards, go back to the base flags.

No server window

--nogui stops the server from opening its graphical window. You type commands in the console window instead. Untick it if you want that window.

Restart loop

With the loop on, the script starts the server again 10 seconds after it exits. That covers crashes, but it also means the stop command no longer ends things: the server comes back. To shut down for good, type stop, wait for the countdown to appear, then press Ctrl+C (on Windows, then answer Y) or close the window.

Which Java version each Minecraft release needs

The script runs whichever java is installed, so the right version has to be on the machine. These are the minimums as of October 2026. The newest release is 26.3, from 15 September 2026.

Java Edition release	Minimum Java
26.1 to 26.3	Java 25
1.20.5 to 1.21.11	Java 21
1.18 to 1.20.4	Java 17
1.17 and 1.17.1	Java 16
1.12 to 1.16.5	Java 8
1.6.1 to 1.11.2	Java 6
1.5.2 and older	Java 5

For 1.16.5 and older, Java 8 is the safe pick: it meets every minimum in those rows, and it is what Mojang's launcher uses for 1.7.2 to 1.16.5. Server software can ask for more: Paper recommends Java 21 for Paper 1.20 to 1.21.11, so check Paper's requirements table if you run Paper. To see what you have, type java -version in a terminal.

Common mistakes

The jar name does not match. Java answers Error: Unable to access jarfile. Copy the exact file name, version numbers included, into the field above.
The file is really start.bat.txt. Windows hides file extensions by default. Turn on file name extensions in File Explorer's View menu and rename the file.
Java is missing or too old. 'java' is not recognized means it is not installed or not on your PATH. An UnsupportedClassVersionError means the installed Java is older than the server needs.
More memory than the machine has. Java stops at startup with an insufficient memory error. Lower the number.

On a managed host you can skip this

A start script only matters when you launch Java yourself. On a managed host the startup command is usually set for you, and the parts you may change sit in the control panel, so you normally have nothing to upload. What carries over is the rest of the setup: build your settings file with the server.properties generator, write the line players see in the server list with the MOTD generator, and once the server is up, test it from outside with the server status checker.

Sources

The data and rules in this tool were last checked on 12 October 2026 against:

Minecraft server start script generator