.NET CLR Error — Application Has Stopped Working (CLR20r3)

Fix .NET CLR errors causing application crashes with CLR20r3 event names, including missing runtime versions, corrupted assemblies, and framework conflicts. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: CLR20r3 is the Watson bucket event name for unhandled .NET exceptions causing crashes. Event Viewer shows the faulting module, exception code, and the .NET method that crashed. Applications may require specific .NET Framework versions (3.5, 4.7.2, 4.8) or .NET 6/7/8 runtime. Missing or corrupted .NET runtime installations are a common cause. Side-by-side .NET installations can conflict if the application targets a specific version. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Required .NET Framework or .NET runtime version not installed. .NET runtime corrupted by a failed Windows Update or incomplete installation. Application targeting a newer .NET version than what is installed. Missing Visual C++ Redistributable required by native dependencies. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Check Event Viewer > Application log for the CLR20r3 event details and exception information. Install the required .NET version: check the application's documentation or error details. Install .NET Framework 3.5: Settings > Apps > Optional Features > .NET Framework 3.5. Install .NET 6/7/8 runtime from https://dotnet.microsoft.com/download. Repair .NET: use the .NET Framework Repair Tool from Microsoft (for Framework 4.x). Install latest Visual C++ Redistributable (x86 and x64) from Microsoft. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Windows Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.