**See also <xref:Mirror.NetworkBehaviour> in the API Reference.**
There are a number of events relating to network behaviours that can occur over the course of a normal multiplayer game. These include events such as the host starting up, a player joining, or a player leaving. Each of these possible events has an associated callback that you can implement in your own code to take action when the event occurs.
When you create a script which inherits from `NetworkBehaviour`, you can write your own implementation of what should happen when these events occur. To do this, you override the virtual methods on the `NetworkBehaviour` class with your own implementation of what should happen when the given event occurs.
This is a full list of virtual methods (callbacks) that you can implement on `NetworkBehaviour`, and where they are called
## Server Only
- OnStartServer
- called when behaviour is spawned on server
- OnStopServer
- called when behaviour is destroyed or unspawned on server
- OnSerialize
- called when behaviour is serialize before it is sent to client, when overriding make sure to call `base.OnSerialize`
- called when behaviour has authority when it is spawned (eg local player)
- called when behaviour is given authority by the sever
- OnStartLocalPlayer
- called when the behaviour is on the local player object
- OnStopAuthority
- called when authority is taken from the object (eg local player is replaced but not destroyed)
- OnStopClient
- called when object is destroyed on client by the `ObjectDestroyMessage` or `ObjectHideMessage` messages
# Example flows
Below is some example call order for different modes
> NOTE: `Start` is called by unity before the first frame, while normally this happens after Mirror's callbacks. But if you dont call ` NetworkServer.Spawn` the same frame as `instantiate` then start may be called first
> Note: `OnRebuildObservers` and `OnSetHostVisibility` is now on `NetworkVisibility` instead of `NetworkBehaviour`
## Server mode
When a NetworkServer.Spawn is called (eg when new client connections and a player is created)
-`OnStartServer`
-`OnRebuildObservers`
-`Start`
## Client mode
When local player is spawned for client
-`OnStartAuthority`
-`OnStartClient`
-`OnStartLocalPlayer`
-`Start`
## Host mode
These are only called on the **Player Game Objects** when a client connects:
