> For the complete documentation index, see [llms.txt](https://fish-networking.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://fish-networking.gitbook.io/docs/guides/features/network-communication/synchronizing/custom-synctype.md).

# Custom SyncType

For example: if you have a data container with many variables you probably don't want to send the entire container when you change it, as a SyncVar would. By making a custom SyncType you can customize the behavior entirely; this is how other SyncType work.

```csharp
/* If one of these values change you
* probably don't want to send the
* entire container. A custom SyncType
* is perfect for only sending what is changed. */
[System.Serializable]
public struct MyContainer
{
    public int LeftArmHealth;
    public int RightArmHealth;
    public int LeftLegHealth;
    public int RightLeftHealth;            
}
```

Custom SyncTypes follow the same rules as other SyncTypes. Internally other SyncTypes inherit from SyncBase, and your type must as well. In addition, you must implement the *ICustomSync* interface.

```csharp
public class SyncMyContainer : SyncBase, ICustomSync
{
    /* If you intend to serialize your type
    * as a whole at any point in your custom
    * SyncType and would like the automatic
    * serializers to include it then use
    * GetSerializedType() to return the type.
    * In this case, the type is MyContainer.
    * If you do not need a serializer generated
    * you may return null. */
    public object GetSerializedType() => typeof(MyContainer);
}

public class YourClass
{
    private readonly SyncMyContainer _myContainer = new();
}
```

Given how flexible a custom SyncType may be there is not a one-size fits all example. You may view several custom examples within your FishNet import under `FishNet/Demos/CustomSyncType`.