World Seed - Terraria Wiki

The World Seed feature enables the display of the random seed used to generate a Terraria world, and allows the player to input a custom seed manually when creating a new world. Worlds generated in 1.3.4 or later will always have a world seed. In 1.3.4, an experimental feature setting was added to allow players to see, copy, and input the world seed. 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 durin

World Seed - Terraria Wiki

Secret seeds now have unique icons in the World Select menu! : r

Best secret world seeds for Terraria 1.4

Ambient objects - Terraria Wiki

PC - SHARE YOUR MAP SEED [PC 1.3.4 & beyond], Page 10

Secret world seeds - Terraria Wiki