Damage Notifications is a plugin that tells the people on your server how they take damage. Every time a player takes damage, a message is sent to them in the chat that tells them what type of damage it was. For example, when someone hits a player, the player receives a message that says "You just took ENTITY_ATTACK damage!"
The plugin's configuration file lets you decide which types of damage will send messages to players.
The pages show you how to configure the plugin.
SpigotMC: https://www.spigotmc.org/resources/damage-notifications.93187/
The Damage Notifications Team
