Externally Referenced warning - what does it mean?

I am curious as to the cause of this error warning:

Warning P_cloud7 ParticleSystemComponent /Game/Maps/Game.Game:PersistentLevel.P_cloud7.ParticleSystemComponent0 : Externally referenced


This is happening in a 4.8.3 project that has been converted to 4.9.1

As of right now documentation is of no help:

If someone has some idea how I can clear these out, please let me know.

Thank you.

it means that one of the oldest and most irritating bugs known to man has not been fixed.
1 close the project.
2 in finder or file manager open the “Unreal Projects” directory
3 rename the projects route folder (yourgame to yourgame1)
4 open the project in the editor
5 file, Save All
6 Close the editor
7 in finder or file manager open the “Unreal Projects” directory again
8 rename the projects route folder back again (yourgame1 to yourgame)
no more externaly referenced warnings


Thanks, that was extremely odd.
Is it the space in “project 4.9.1” ? I renamed directory to project491 and everything resolved.

This seems to occur when opening a copy of your project in a new editor version since this changes the name of your project folder. Change the name back to the original folder name and the errors should be gone.

I agree, resetting “Project Folder name” to “Name of .uproject file” at once solved the issue.

Doesn’t work with 4.12 preview.

JM_Lovermind, make sure the maps referenced in your project settings are not still pointing to 4.11.x location.

mxnko You are right, change [project_name 4.12] to [project_name 4.11] solves the problem… However, the procedure is different compared to older versions … where it was enough to change only the name of the folder, open the project, save & rename…
What is your solution?

For those, like myself, wondering what exactly is going on, I debugged through this. While there might be multiple scenarios that lead to this bug, I believe they are similar to the following:

  1. In the file, ******\Saved\Config\Windows\Engine.ini , in the section “[Core.System]”, there are a list of Paths. These are content paths. They might look something like this:





  2. When opening a level, the engine does an “external reference” check by verifying that content/assets are within one of the above paths.

  3. Sometimes during project conversions, the project converter doesn’t properly update the personal content path above ("… MyProject/Content" above). If the path to the content changed during a conversion, but the above path(s) in engine.ini weren’t correspondingly changed, the engine would be performing its “external reference check” against the wrong paths. Hence, the engine will claim an object is externally referenced, when it is not.

  4. (1) Closing the project, (2) changing an outer folder name of the project, and (3) re-opening the project DOES cause the engine to properly update the paths in engine.ini, which is why people suggest renaming the project’s outer folder to resolve the issue. Changing the outer folder name back to the original name is optional, and is only needed if you prefer the original path name.

Finally someone explaining the magic trick …

Please how you solved it? I have the same issue with 4.12 and my copied project fro 4.11…

Hi StMalk your answer is right below from Directx77.
You just only change path in Engine.ini (“Core.System” section)

Thanks a lot guys… :slight_smile:

Nice work of debugging, this helped me a lot, but you can also just delete the saved folder where this file is located. When starting your project, it gets generated again and any reference errors should be fixed :slight_smile:

Thanks for info about Engine.ini, I’ve had this bug when I moved my game proj directory + deleted epic launcher completely(included everything in documents), all I had to do to fix this, is to remove Engine.ini from “Saved\Config\Windows”, then, editor will recreate this ini, with right paths when you start your project, now Engine.ini paths to my games dir is"%GAMEDIR%Content" and not “…/…/…/”.

Important note for anyone still experiencing this issue after trying all of the above: Try deleting your ‘Saved’ folder in your project files. This worked for me after the rename trick failed, likely because I copied my whole project from another computer, and then upgraded to a newer version.

Just putting this out there since whenever I googled the problem, this thread came up first.

Directx77 Thanks!!!
This has been bugging me for months!

thanks ill try this immediately great man

Thanks, this was the solution.

For me in 4.18 this was the solution, but you can just delete Saved/Config, you don’t have to delete all of your Saved Folder

I recommend keeping your EditorPerProjectUserSettings.ini (folder colorings, BP context menu favorites, etc)

Thank you for posting this!

blood pressure dropping rapidly now