level-type=minecraft:flat, then generate a new world. This setting does not flatten chunks that already exist.
1
Back up the current world
Create a server backup. A fresh flat world does not contain the builds or player progress from the current world.
2
Stop the server
Wait for a clean shutdown before editing files.
3
Change the world type
Open
server.properties and set:4
Generate a fresh world
Follow Reset a Java world, then start the server. The setting applies when the new world generates.
5
Verify the result
Join the server and confirm that new terrain uses the flat preset.
level-type=minecraft:normal and generate another fresh world. Changing the property alone does not rebuild existing chunks.