An “ApplicationException: Unable to find a suitable compiler” Error in Unity3D

When we try to manipulate our assets, we can get the error:

ApplicationException: Unable to find a suitable compiler

UnityEditor.Scripting.ScriptCompilers.CreateCompilerInstance (MonoIsland island, Boolean buildingForEditor, BuildTarget targetPlatform) (at C:/BuildAgent/work/xxxxxxxxxxxxxxxx/Editor/Mono/Scripting/ScriptCompilers.cs:XX)

And you can’t run “Play” button.

Of course, we can use

Assets -> Reimport All

But does it help you every time you run this command? You wait, wait, and wait for the end of importing. And always the same! You see the error.

I got the error too. And I started to search the problem in my assets. And now I know that if you see such an error, just look into your Assets folder in your Unity project. Remember:

No libraries (that are .dll files in Windows) should be in the Assets folder!!!

And you should remove all directories that contain libraries from the Assets folder. It’s the problem that cause this error. All the libraries must be outside this folder. It’s only for assets.