How to Change Your Minecraft World Seed
Generate a new world with a specific seed or let the server pick a random one.
Understanding World Seeds
A world seed is a string that Minecraft uses to generate the world terrain. The same seed always produces the same world - same biomes, same structures, same ore distribution.
If you leave level-seed blank in Settings, the server generates a random seed the first time it creates the world. After that the seed lives in level.dat and cannot be changed for that world.
To use a specific seed, you must set it before the world is generated. If a world already exists, changing level-seed has no effect - the server uses the seed stored in the existing world data.
Changing the Seed
To generate a new world with a different seed:
1. Take a backup from the Backups tab - "Create Backup Now". This is the only way back to the old world.
2. Stop the server.
3. In the Settings tab, set level-seed to the seed you want. Leave it blank for a random one. This is a restart-required setting, so if the server were running the panel would restart it for you.
4. Delete the world in the Files tab. On 26.2 all three dimensions live inside the one <level-name> folder (default "world"), under dimensions/minecraft/, on every server type - so that single folder is the whole world. A Paper server carried over from an earlier version can still have leftover <level-name>_nether and <level-name>_the_end folders beside it; delete those too if they are there.
5. Start the server. It generates a new world with your seed.
If any world folder survives, the server loads what is there and ignores the new seed.
The Admin tab's "Delete Savegames" does the same job without hunting through folders - it removes save data and leaves game files and settings alone.
World Type Options
You can also change the world type with level-type in the Settings tab:
minecraft:normal - Default terrain generation with varied biomes.
minecraft:flat - Superflat world. Good for building or testing.
minecraft:large_biomes - Normal terrain but with larger biomes.
minecraft:amplified - Extreme terrain with huge mountains. Demands more RAM and CPU.
minecraft:single_biome - One biome everywhere. Which biome it is comes from the world generator settings, not from this field.
Change level-type at the same time you change the seed (and delete the old world). The world type only applies on world generation.
Verifying the Seed
After joining the new world, type /seed in chat. The server prints the world seed. Verify it matches what you set in server.properties.
If the seed does not match, part of the old world survived - on Paper, check for leftover <level-name>_nether and <level-name>_the_end folders as well - or the setting was not saved before the server started.
Share the seed with your players if you want them to be able to find specific locations using external tools like Chunk Base.