How to use a custom world seed

A seed decides how your world generates: the same seed always produces the same terrain, villages and structures. Using a specific one lets you start on a map you have already seen.

A seed only applies to a brand new world

This is the part that catches people out. The seed is read once, when a world is first generated. Setting a seed on a server that already has a world does nothing at all: Minecraft finds the existing world folder and loads it, seed or no seed.

To use a new seed you have to give the server no world to load, either by resetting the current one or by starting a new world under a different name.

Set a seed on a fresh world

1. Back up first if you care about the current world. Once it is gone it is gone. See Back up and restore your world.
2. Reset the world so there is nothing to load, following How to reset your world.
3. Open the Files tab and edit server.properties.
4. Put your seed after the equals sign, for example level-seed=123456789.
5. Save the file and Start the server. It generates the new world as it boots, which takes a little longer than a normal start.

Creating a brand new server instead? You can type the seed straight into the wizard's world step and skip all of this.

Notes on seeds

• Seeds can be numbers or words. glacier is a valid seed; so is -4172144997902289642.
• Paste it exactly as shown, including any minus sign. A different seed gives a completely different map.
• The same seed only matches for the same Minecraft version. Terrain generation changes between versions, so a 1.20 seed will not look identical on 1.21.