Synchronizing Prefab Instances via PrefabUtility

In this lesson, you will learn how to use the PrefabUtility API to programmatically push changes from a specific scene instance back to its source Prefab asset, ensuring your project data stays consistent.

Why use PrefabUtility?

Usually, when you change a Prefab instance in your scene, Unity marks those changes as "Overrides." If you want those changes to become the new default for every other instance of that Prefab in your project, you would normally click the "Apply All" button in the Inspector. PrefabUtility allows you to perform this "Apply" action through your own custom scripts or editor tools.

This is incredibly useful if you have a workflow where, for example, a script automatically updates the health values or material properties of 100+ instances and you want to save those values back to the original source file.

Applying Changes Programmatically

To apply changes, you use the PrefabUtility.ApplyPrefabInstance method. This method takes the instance you are modifying and the InteractionMode (which tells Unity if we are doing this in the normal scene view or an isolated context).

Here is a quick example of how you might push changes from a specific instance back to its asset:

using UnityEditor;
using UnityEngine;

public class PrefabUpdater : MonoBehaviour
{
    public void SaveInstanceChanges(GameObject instance)
    {
        // Get the path to the original asset
        string assetPath = PrefabUtility.GetPrefabAssetPathOfNearestInstanceRoot(instance);
        
        // Push the changes from the instance back to the prefab asset
        PrefabUtility.ApplyPrefabInstance(instance, InteractionMode.UserAction);
        
        Debug.Log($"Changes synced to {assetPath}");
    }
}

Important Considerations

When you call ApplyPrefabInstance, you are fundamentally changing the source asset. This is a destructive action for other instances, as they will immediately adopt the new values. Always ensure that your logic validates which instance is the "source of truth" before pushing updates. By utilizing PrefabUtility, you can automate complex data migrations across your project without needing to manually click through the Inspector for every single object.

Key Takeaway: Use PrefabUtility.ApplyPrefabInstance to programmatically save scene-level overrides back to your source Prefab assets, ensuring consistent data synchronization throughout your project.