# SyncVars

SyncVars are properties of classes that inherit from NetworkBehaviour, which are synchronized from the server to clients. When a game object is spawned, or a new player joins a game in progress, they are sent the latest state of all SyncVars on networked objects that are visible to them. Use the `SyncVar` custom attribute to specify which variables in your script you want to synchronize.

The state of SyncVars is applied to game objects on clients before `OnStartClient()` is called, so the state of the object is always up-to-date inside `OnStartClient()`.

SyncVars can use any [type supported by Mirror](../Guides/DataTypes.md). You can have up to 32 SyncVars on a single NetworkBehaviour script, including SyncLists (see next section, below).

The server automatically sends SyncVar updates when the value of a SyncVar changes, so you do not need to track when they change or send information about the changes yourself.

>   The [SyncVar hook](SyncVarHook.md) attribute can be used to specify a method to be called when the SyncVar changes value on the client.

## SyncVar Example

Let's say we have a networked object with a script called Enemy:

``` cs
public class Enemy : NetworkBehaviour
{
    [SyncVar]
    public int health = 100;

    void OnMouseUp()
    {
        NetworkIdentity ni = NetworkClient.connection.playerController;
        PlayerController pc = ni.GetComponent<PlayerController>();
        pc.currentTarget = gameObject;
    }
}
```

The `PlayerController` might look like this:

``` cs
public class PlayerController : NetworkBehaviour
{
    public GameObject currentTarget;

    void Update()
    {
        if (currentTarget != null)
            if (currentTarget.tag == "Enemy")
                if (Input.GetKeyDown(KeyCode.X))
                    CmdShoot(currentTarget);
    }

    [Command]
    public void CmdShoot(GameObject enemy)
    {
        enemy.GetComponent<Enemy>().health -= 5;
    }
}
```

In this example, when a Player clicks on an Enemy, the networked enemy game object is assigned to `PlayerController.currentTarget`.  When the player presses X, with a correct target selected, that target is passed through a Command, which runs on the server, to decrement the `health` SyncVar.  All clients will be updated with that new value.  You can then have a UI on the enemy to show the current value.