How to change the difficulty of a Minecraft server

There are four difficulties: peaceful, easy, normal and hard. Change it with a command or in the file.

With a command

In the console or as an operator in the game:

/difficulty hard

It takes effect at once and is saved with the world.

In server.properties

difficulty=normal

This is the setting for a new world. For an existing world the saved difficulty wins, so use the command. On Saryno the Settings page does both at once.

What each does

	Hostile mobs	Hunger	Notes
Peaceful	None	Never drains	Health comes back
Easy	Yes, weaker	Can drain to 5 hearts	Good for new players
Normal	Yes	Can drain to 1 heart	The default
Hard	Yes, stronger	Can starve to death	Zombies break doors

Hardcore

hardcore=true is set when the world is made. Players who die are put in spectator mode (or banned if configured). It cannot be switched on later in the same way, so decide before you start.

Locking it

/difficulty can be changed by any operator, and a plugin like Multiverse can set a different difficulty per world. See commands for owners and server.properties explained.