World Seed

The World Seed feature enables the display of the random seed used to generate a Terraria world, and allows the user to input a custom seed manually when generating a new world.

Worlds generated with Terraria 1.3.4 and later will always have a seed regardless of settings; The experimental feature setting merely allows the user to see, copy, and input them. If a seed is not entered manually during world generation, a seed is automatically generated randomly. Worlds generated prior to 1.3.4 will never have a viewable seed: while they were generated with a random seed, that information was only used during world creation, and was not stored in the world file.

Worlds created after 1.4.0.1 will always be able to have their seeds edited upon world creation, regardless of the experimental feature setting.

Some secret world seeds have been discovered as easter eggs that generate worlds with strange and unique features.

Copying seeds from created worlds
Worlds with a seed display a small seed icon in the world list, allowing the user to see that world's seed and copy it to their computer's clipboard. A copied seed can then be input when generating a new world, which results in a nearly identical generated world, provided it is generated with identical parameters (same size, same choice between Corruption and Crimson, and same choice of difficulty).

World seeds are formatted like this:.

Size:
 * 1, if World size is Small.
 * 2, if World size is Medium.
 * 3, if World size is Large.

Difficulty:
 * 1, if World Difficulty is Classic.
 * 2, if World Difficulty is Expert.
 * 3, if World Difficulty is Master.
 * 4, if World Difficulty is Journey.

World evil:
 * 1, if World Evil is Corruption.
 * 2, if World Evil is Crimson.

Identifier: The actual unique random seed.

This formatting can be used to automatically set all the initial settings of a world to be as desired.

History
世界种子