What Is It?

• An attribute provided by Unity that automatically invokes a method before or after a Scene is loaded when the app starts
• You don’t need to inherit from MonoBehaviour — it works with a static method
• The return type must always be void

What Settings Are There?

SubsystemRegistration

• Used to reset global static state
• Mainly used to reset state values when developing with Domain Reload disabled via Enter PlayMode
• The stage for cleaning up anything that might have leftover values from the previous runtime
• Not suitable for MonoBehaviour-based types

AfterAssembliesLoaded

• After preload asset initialization, but before scene initialization
• The Assembly-level processing stage for DI injection, reflection-based registration, attribute scanning, etc.
• Also not suitable for MonoBehaviour-based types

BeforeSplashScreen

Try not to use this stage at all — just forget it exists. Doing anything here only increases boot complexity.

• Called just before the splash screen appears, before the first scene is loaded
• Early native/platform initialization
• Bootstrap calls before the splash screen
• That said, avoid this enum value as much as possible

BeforeSceneLoad

• The first scene has been loaded, but Awake has not yet been called
• Objects are in an inactive state
• Good for creating static services that need to be ready before Awake runs
• Injecting configuration values before entering a scene
• Great for preparing anything that components in the scene will use
• Finding objects via FindObjectType, etc. may be difficult at this point

AfterSceneLoad

• The default value for RuntimeInitializeOnLoadMethod
• Called immediately after Awake and OnEnable have finished
• A good stage for organizing and linking MonoBehaviour-derived objects

But…

I like building Unity Packages, and I was calling this method from inside a Package. It worked fine in the Editor, but it wasn’t being called in Android and iOS builds. Why?!

After Looking Into It…

On Android and iOS, IL2CPP’s Managed Stripping removes unused code. My code was wrapped in #if UNITY_ANDROID and #if UNITY_IOS conditionals, which apparently caused it to be stripped.

So I created an empty .cs file and added:

[assembly: AlwaysLinkAssembly]

This is an Assembly-level keyword that prevents the code from being stripped.

What Is AlwaysLinkAssembly?

It’s an attribute that forces Unity’s IL2CPP Managed Stripping process to never remove the assembly — even if there are no direct references to it.

And with that… everything was resolved!