"Unable to instantiate prefab. Prefab may be broken"

Hey there ! I just upgraded my project from 2017.3 to 2018.1 and now all of my scenes are broken (missing prefab for every object) and when I try to drag’n drop a prefab into the scene I get the following error :

Unable to instantiate prefab. Prefab may be broken.
UnityEditorInternal.InternalEditorUtility:HierarchyWindowDrag(HierarchyProperty, Boolean, HierarchyDropMode)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

So my scenes are broken and I can’t add any prefab … Any idea ?

  1. open *.Prefab in Text Editor (need modify unity editor setting)
  2. change text “m_SourcePrefab” to “m_ParentPrefab”
  3. change text “m_IsPrefabAsset” to “m_IsPrefabParent”
    it ok, try.
    if your unity other version, can you create empty GameObject then compare difference.

So, 2018.2 made some changes to prefabs that break things when you try to downgrade. I’ve found two solutions, but I’ve only tried the first.

No matter what you do, make sure you’ve backed up your project first.

Solutions

  1. Break the prefabs in the 2018.2+, in your scene. SAVE your scene. Then open that scene in the older Unity version (either by exporting and importing, or by copying your project or files). The prefabs that are in the scene, that you broke the connection should still work. You can break a prefab in the “GameObject” menu after selecting a prefab.
    There’s some more info here Missing prefabs after downgrading from Unity 2018.2.0b2 to 2018.1.0f2 - Questions & Answers - Unity Discussions

  2. You can try modifying the files themselves from the console as outline here Reddit - Dive into anything

Be aware that other things may break also, when downgrading(which is my problem, right now).

hey Guys! the solution for that is (Right click on the prefab and then hit Reimport)

This is most likely the same issue as in this question over here. The problem is that Unity seems to have changed it’s prefab serialization format and didn’t make it backward nor forward compatible. It’s mainly a rename of some fields. If you use text serialization you could rename those fields yourself. However i strongly recommend you create a backup of your project.

Also if you can verify that this is the problem, please file a bug report with as many details possible. So create a new standalone project where you copy that offending prefab to and attach that project to the bugreport. The more people verifying the issue, the faster this may be fixed.

As a general advice: If you are in the middle of a production, do not upgrage Unity. Even Unity doesn’t recommend it.

If you have make a backup you can download unity hub and run your project with Unity 2017.3.

Same page…
Any thought? I’ve already tried to export from U2018 but no luck.

I get this problem often its so annoying. I downloaded an asset other day and tried it. Everything went fine and i didnt touch that asset folder in my project since then was working on something else. Then i come back couple days or week later and try to place a prefab on the scene bam broken. Nothing changed at all. Unity often randomly give bug like this using 2018.1.1f1. It happened with many other asset. When its not its a script in my scene that get unlinked for some reason. I think i lost a whole week since 2 month trying to figure out bugs that was related to broken prefabs or missing script that randomly appear. Is there a known unity version working at best? Im gonna give it a try.

I’m having the same issue, and I can’t find anything related on the issue tracker.

One thing I noticed is that I just downloaded 2018.2, and my prefabs are working again.

  1. Started with a project with prefabs in 2017.3
  2. Opened in 2018.1, saved and closed
  3. Opened project from 2018.1 format in 2018.2, and now my prefabs work again
  1. In the ‘Hierarchy’ view in the top menu select ‘Create Empty’.
  2. Right-click on the new game object in the Inspector and reset the ‘Transform’.
  3. From the ‘Hierarchy’, drag the game object into your ‘Project’ view (which creates a new empty prefab).
  4. Now take the problem prefab in the ‘Project’ view and drag it over-top of the new empty prefab.
  5. You will be asked: 'Are you sure you want to replace the contents…" Click ‘Replace Anyway’.
  6. The new prefab is replaced and updated using the old one, and should now work.
  7. Delete the old broken prefab.

Same problem here