Seed

A seed is the starting value of Minecraft’s world generator. Terrain, biomes and structure positions are all calculated from it. Given the same seed and the same Minecraft version and world settings, the generator produces the same world.

Seeds are 64-bit numbers. You can also type text as a seed; the game converts it into a number.

Setting a seed on a server

The seed is set with level-seed in server.properties. If it is empty, the server picks a random one. The setting only has an effect when a new world is created. To start a fresh world with a new seed, stop the server, move or delete the old world folder (after a backup), set the seed and start again.

Operators can see the current world’s seed in game with /seed.

Changing the seed later

Changing level-seed for an existing world does not regenerate what already exists. Only chunks generated from then on use the new seed, which creates hard edges where old and new terrain meet. The same happens when you update to a Minecraft version with different world generation: existing chunks stay, new ones follow the new generator.

Why it matters for server owners

• Players often ask for a specific seed they found online; check which Minecraft version that seed was shared for, since the same seed can look very different across versions.
• Anyone who knows your seed can find structures and resources with seed map tools. On competitive or survival servers you may want to keep it private.
• Custom world generation from datapacks or mods also changes the result for a given seed.

Practical tip

Decide on seed and world generation before opening the server, then pre-generate the area players will use. Changing either afterwards always leaves visible borders.