Name Tag

A name tag is an item used to name mobs in the world.

Fishing
Name tags can be caught from fishing as part of the treasure category with a 14% chance after the 5% chance of being a treasure catch. The chance of catching treasure increases with the Luck of the Sea enchantment.

Trading
Master-level librarian villagers sell a name tag for 20 emeralds as part of their trade.

Usage
To use a name tag, it must first be renamed with an anvil, costing 1 experience level.

If it is not renamed, it has no effect when used on a mob. After the name tag is renamed, the player can it on a mob to give it the name given to the name tag from the anvil. Mobs and name tags can be renamed any number of times. Name tags with the same name are stackable.

Once a mob is named, it keeps its name and the name tag disappears. (A named silverfish that goes into a block appears to lose its name because it is replaced by a newly-generated un-named silverfish when the block is broken.)

A baby (animal or villager) keeps its name when becoming an adult. A named villager keeps its name when transformed into a zombie villager, and a named zombie villager keeps its name when cured.

When a mob is named, it does not count toward the mob cap.

Limitations
Any mob can be named except for the ender dragon and players.

A name tag can rename an armor stand, though it does not show the nameplate above its head until  is set as an extra step.

a name tag on a villager renames the villager instead of opening the trading interface. A saddled pig is renamed instead of being ridden. Using a name tag on any other mob that can be interacted with performs the action instead of being named. These mobs can be renamed if the player uses the name tag while crouching or standing in a nether portal because the portal suppresses the action.

Behavior
Renamed mobs have their name displayed over their head in the fashion as a mob named through a renamed spawn egg. Their names can be seen only if they are aimed at from four or fewer blocks away.

Mobs that are named using the name tag also never despawn in the world, similar to tamed mobs. The exceptions are wandering traders or if the mob is hostile and the difficulty is switched to "Peaceful".

If a renamed mob kills a player, the custom name is used in the death message in place of the mob type name.

A renamed wither also has a renamed health bar.

Easter eggs

 * Any mob that receives the name "Dinnerbone" or "Grumm" is rendered upside down.
 * Naming a sheep "jeb_" causes its wool to fade between the dye colors, producing a rainbow effect. The wool that drops when the sheep is sheared or killed is the original color of the sheep before the sheep was named.
 * Naming a rabbit "Toast" causes it to have a special memorial skin.
 * Naming a vindicator "Johnny" causes it to be aggressive with all mobs (except other illagers).

Trivia

 * Name tags were added at the request of Paulsoaresjr.
 * A stack of up to 64 name tags can be renamed at once. The cost is 1 experience level per stack, regardless of how many name tags were stacked.
 * To name a mob “Name Tag” the player must give the name tag a random name, then rename it back to “Name Tag”.
 * A Villager with a name tag turned into a zombie by a zombie with a name tag does not despawn, but a villager with a name tag turned into a zombie by a zombie without a name tag does despawn.