Unity uses its own serialization system, which is specifically designed to operate efficiently at runtime. Because of this, serialization in Unity behaves differently to serialization in other programming environments.
Unity supports the standard .NET/C# [Serializable] and [NonSerialized] attributes, but their behavior in Unity is subject to additional Unity-specific considerations. Unity won’t automatically serialize a class marked [Serializable] unless it meets the Unity serialization rules outlined in the following sections.
Unity automatically serializes built-in Unity types that inherit from UnityEngine.Object, so you only need to apply [Serializable] to custom classes or structs used as fields in these Unity objects. The [NonSerialized] attribute is used in Unity as in standard C# to exclude fields from serialization. However, in the Unity context this also prevents the InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary from serializing or displaying that field. Unity has its own attribute, [HideInInspector], which hides the field in the Inspector without preventing serialization.
Serializers in Unity work directly on the fields of your C# classes rather than their properties, so Unity only serializes your fields if they meet certain conditions. The following section outlines how to use field serialization in Unity.
To use field serialization you must ensure that the field:
public, or has a [SerializeField] attribute
private fields are serialized, refer to Hot reloading
static
const
readonly
[Serializable] attribute.[Serializable] attribute. (Refer to Serialization of custom classes).List<T> of one of the previously listed field types. With default serialization by value, if one element appears in a list or array twice, the serialized version of the collection will have two copies of that element, rather than one copy that appears twice. When serializing a collection of classes by reference, multiple references to the same object are preserved. For more information, refer to the [SerializeReference] API documentation.Note: Unity doesn’t support serialization of multilevel types (multidimensional arrays, jagged arrays, dictionaries, and nested container types). If you want to serialize these, you have two options:
For Unity to serialize a custom class, you must ensure the class:
[Serializable] attribute.When you assign an instance of a UnityEngine.Object-derived class to a field and Unity saves that field, Unity serializes the field as a reference to that instance. Unity serializes the instance itself independently, so it isn’t duplicated when multiple fields are assigned to the instance. But for custom classes which don’t derive from UnityEngine.Object, Unity includes the state of the instance directly in the serialized data of the MonoBehaviour or ScriptableObject that references them. There are two ways that this can happen: inline and by [SerializeReference].
[SerializeReference] on the field that references the class. This means that if you store a reference to an instance of a custom class in several different fields, they become separate objects when serialized. Then, when Unity deserializes the fields, they contain different distinct objects with identical data.[SerializeReference] serialization: If you do specify [SerializeReference], Unity establishes the object as a managed reference. The host object still stores the objects directly in its serialized data, but in a dedicated registry section.
[SerializeReference] adds some overhead but supports the following cases:
[SerializeReference], then they become separate objects when serialized.[SerializeReference] Unity only serializes the fields that belong to the parent class. When Unity deserializes the class instance, it instantiates the parent class instead of the derived class.
Note: Inline serialization is more efficient, and you should use it unless you specifically need one of the features that [SerializeReference] supports. For full details on how to use [SerializeReference], refer to the SerializeReference documentation.
Unity doesn’t normally serialize properties except in the following situations:
public int MyInt
{
get => m_backing;
private set => m_backing = value;
}
[SerializeField] private int m_backing;
public int MyInt { get; set; }
If you don’t want Unity to serialize a property with auto-generated fields, use the [field: NonSerialized] attribute.