Data IDs

Every item, NPC and block has its own identification number, aka ID, and this page is to tell you what those IDs are, so you don't need to ask for them from other players or spam the forums.

A Mob/Item is missing from the list! What can I do?
This means that either the item/monster is saved in the Terraria client with its name, instead of ID, or it was added in a recent update and the page hasn't been updated yet. For example, items such as Gold Pickaxe and monsters such as Pinky and a few other colored slimes, are saved with their name, and can't be indexed with an ID.

What do I need these IDs for?
Basically, these IDs are used to index monsters or items in Terraria.