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Error: Unity Could Not Load NiceIO

Understanding the "Unity Could Not Load NiceIO" Error

This error typically occurs when using Unity's Package Manager, particularly with packages that depend on NiceIO, such as the Unity Test Framework.

Root Cause

The primary cause of this error is usually an outdated version of the NuGet package for NiceIO in your Unity project.

Solution - How to Resolve It

To fix the "Unity Could Not Load NiceIO" error, follow these steps:

  1. Close Unity: Ensure all instances of Unity are closed.

  2. Locate the NuGet Packages Folder:

    • Navigate to your Unity project folder.
    • Find the Library/PackageCache directory.
  3. Delete NiceIO Package:

    • Look for a folder named com.unity.ide.rider@<version>.
    • Inside this folder, find and delete the lib/JetBrains.Rider.PathLocator.dll file.
  4. Clear Unity Cache (Optional but recommended):

    • Delete the entire Library folder in your Unity project.
  5. Reopen Unity:

    • Launch Unity and open your project.
    • Unity will regenerate the necessary files and should now load NiceIO correctly.
  6. Update Packages (If the error persists):

    • In Unity, go to Window > Package Manager.
    • Update all packages, especially the Test Framework and IDE packages.


To prevent this issue in the future:

  • Regularly update your Unity version and packages.
  • Be cautious when manually modifying package files or the PackageCache directory.

If the problem persists after these steps, consider creating a new Unity project and gradually migrating your assets and scripts to isolate the issue.

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