# RuntimeInitializeOnLoadMethodAttribute

> Use this attribute to get a callback when the runtime is starting up and loading the first scene.

## Definition

* **Type:** Class
* **Namespace:** [UnityEngine](/engine/6000.0/script-reference/unityengine.md)
* **Assembly:** UnityEngine.CoreModule
* **Inherits from:** [PreserveAttribute](/engine/6000.0/script-reference/unityengine/scripting/preserveattribute.md)
* **Implements:** [\_Attribute](https://learn.microsoft.com/dotnet/api/system.runtime.interopservices._attribute)

```csharp
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
public class RuntimeInitializeOnLoadMethodAttribute : PreserveAttribute, _Attribute
```

## Remarks

Use the various options for [RuntimeInitializeLoadType](/engine/6000.0/script-reference/unityengine/runtimeinitializeloadtype.md) to control when the method is invoked in the startup sequence.

The following list shows the execution order of the [RuntimeInitializeLoadType](/engine/6000.0/script-reference/unityengine/runtimeinitializeloadtype.md) callbacks:

1. First various low level systems are initialized (window, assemblies, gfx etc.)
2. Then **SubsystemRegistration** and **AfterAssembliesLoaded**  callbacks are invoked.
3. More setup (input systems etc.)
4. Then **BeforeSplashScreen**  callback is invoked.
5. Now the first scene starts loading.
6. Then **BeforeSceneLoad** callback is invoked. Here objects of the scene is loaded but Awake() has not been called yet. All objects are considered inactive here.
7. Now Awake() and OnEnable() are invoked on MonoBehaviours.
8. Then **AfterSceneLoad** callback is invoked. Here objects of the scene are considered fully loaded and setup. Active objects can be found with FindObjectsByType.

The above details are when starting up a Player build. When entering Play mode in the Editor the same invocations are ensured.

The default callback invocation time is [RuntimeInitializeLoadType.AfterSceneLoad](/engine/6000.0/script-reference/unityengine/runtimeinitializeloadtype/aftersceneload.md). The execution order within each of the [RuntimeInitializeLoadType](/engine/6000.0/script-reference/unityengine/runtimeinitializeloadtype.md) callbacks is not guaranteed.

**Note:** Use the [AlwaysLinkAssemblyAttribute](/engine/6000.0/script-reference/unityengine/scripting/alwayslinkassemblyattribute.md) on package or precompiled assemblies that contain one or more methods with the `[RuntimeInitializeOnLoadMethod]` attribute, but which may not contain types used directly or indirectly in any scenes built for the project.

Additional Resources: [Managed code stripping](/engine/6000.0/manual/scripting/compilation-and-code-reload/script-compilation/managed-code-stripping.md)

## Examples

```csharp
// Demonstration of the RuntimeInitializeOnLoadMethod attribute
using UnityEngine;

class MyClass
{
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSplashScreen)]
    static void OnBeforeSplashScreen()
    {
        Debug.Log("Before SplashScreen is shown and before the first scene is loaded.");
    }

    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    static void OnBeforeSceneLoad()
    {
        Debug.Log("First scene loading: Before Awake is called.");
    }

    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterSceneLoad)]
    static void OnAfterSceneLoad()
    {
        Debug.Log("First scene loaded: After Awake is called.");
    }

    [RuntimeInitializeOnLoadMethod]
    static void OnRuntimeInitialized()
    {
        Debug.Log("Runtime initialized: First scene loaded: After Awake is called.");
    }
}
```

## Constructors

| Constructor                                                                                                                                                                                                                                     | Description                                                                                                                                            |
| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ |
| [RuntimeInitializeOnLoadMethodAttribute()](/engine/6000.0/script-reference/unityengine/runtimeinitializeonloadmethodattribute/ctor.md#runtimeinitializeonloadmethodattribute\(\))                                                               | Use the [RuntimeInitializeLoadType](/engine/6000.0/script-reference/unityengine/runtimeinitializeloadtype.md) to control when the callback is invoked. |
| [RuntimeInitializeOnLoadMethodAttribute(UnityEngine.RuntimeInitializeLoadType)](/engine/6000.0/script-reference/unityengine/runtimeinitializeonloadmethodattribute/ctor.md#runtimeinitializeonloadmethodattribute\(runtimeinitializeloadtype\)) | Use the [RuntimeInitializeLoadType](/engine/6000.0/script-reference/unityengine/runtimeinitializeloadtype.md) to control when the callback is invoked. |

## Properties

| Property                                                                                                   | Description                              |
| ---------------------------------------------------------------------------------------------------------- | ---------------------------------------- |
| [loadType](/engine/6000.0/script-reference/unityengine/runtimeinitializeonloadmethodattribute/loadtype.md) | Controling the callback invocation time. |

## Inheritance

**Inherited Members:**

* [Attribute.GetCustomAttributes(MemberInfo, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-memberinfo-system-type\))
* [Attribute.GetCustomAttributes(MemberInfo, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-memberinfo-system-type-system-boolean\))
* [Attribute.GetCustomAttributes(MemberInfo)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-memberinfo\))
* [Attribute.GetCustomAttributes(MemberInfo, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-memberinfo-system-boolean\))
* [Attribute.IsDefined(MemberInfo, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-memberinfo-system-type\))
* [Attribute.IsDefined(MemberInfo, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-memberinfo-system-type-system-boolean\))
* [Attribute.GetCustomAttribute(MemberInfo, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-memberinfo-system-type\))
* [Attribute.GetCustomAttribute(MemberInfo, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-memberinfo-system-type-system-boolean\))
* [Attribute.GetCustomAttributes(ParameterInfo)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-parameterinfo\))
* [Attribute.GetCustomAttributes(ParameterInfo, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-parameterinfo-system-type\))
* [Attribute.GetCustomAttributes(ParameterInfo, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-parameterinfo-system-type-system-boolean\))
* [Attribute.GetCustomAttributes(ParameterInfo, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-parameterinfo-system-boolean\))
* [Attribute.IsDefined(ParameterInfo, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-parameterinfo-system-type\))
* [Attribute.IsDefined(ParameterInfo, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-parameterinfo-system-type-system-boolean\))
* [Attribute.GetCustomAttribute(ParameterInfo, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-parameterinfo-system-type\))
* [Attribute.GetCustomAttribute(ParameterInfo, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-parameterinfo-system-type-system-boolean\))
* [Attribute.GetCustomAttributes(Module, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-module-system-type\))
* [Attribute.GetCustomAttributes(Module)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-module\))
* [Attribute.GetCustomAttributes(Module, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-module-system-boolean\))
* [Attribute.GetCustomAttributes(Module, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-module-system-type-system-boolean\))
* [Attribute.IsDefined(Module, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-module-system-type\))
* [Attribute.IsDefined(Module, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-module-system-type-system-boolean\))
* [Attribute.GetCustomAttribute(Module, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-module-system-type\))
* [Attribute.GetCustomAttribute(Module, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-module-system-type-system-boolean\))
* [Attribute.GetCustomAttributes(Assembly, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-assembly-system-type\))
* [Attribute.GetCustomAttributes(Assembly, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-assembly-system-type-system-boolean\))
* [Attribute.GetCustomAttributes(Assembly)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-assembly\))
* [Attribute.GetCustomAttributes(Assembly, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattributes#system-attribute-getcustomattributes\(system-reflection-assembly-system-boolean\))
* [Attribute.IsDefined(Assembly, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-assembly-system-type\))
* [Attribute.IsDefined(Assembly, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.isdefined#system-attribute-isdefined\(system-reflection-assembly-system-type-system-boolean\))
* [Attribute.GetCustomAttribute(Assembly, Type)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-assembly-system-type\))
* [Attribute.GetCustomAttribute(Assembly, Type, bool)](https://learn.microsoft.com/dotnet/api/system.attribute.getcustomattribute#system-attribute-getcustomattribute\(system-reflection-assembly-system-type-system-boolean\))
* [Attribute.Equals(Object)](https://learn.microsoft.com/dotnet/api/system.attribute.equals)
* [Attribute.GetHashCode()](https://learn.microsoft.com/dotnet/api/system.attribute.gethashcode)
* [Attribute.Match(Object)](https://learn.microsoft.com/dotnet/api/system.attribute.match)
* [Attribute.IsDefaultAttribute()](https://learn.microsoft.com/dotnet/api/system.attribute.isdefaultattribute)
* [Attribute.TypeId()](https://learn.microsoft.com/dotnet/api/system.attribute.typeid)