Error while trying to run project: Unable to start debugging on the web server

If while trying to debug your ASP.NET web application you receive the following error:

Error while trying to run project: Unable to start debugging on the web server. Catastrophic failure.
Would you like to disable future attempts to debug ASP.NET pages for this project?

You most probably don’t have ASP.NET registered correctly on the system in which you are trying to make the debugging. Open Run from Start Menu -> Run and type the following line:

aspnet_regiis.exe -i

After ASP.NET is registered successfully, reset IIS using the following command once again inside Run:


For more details read the tutorial entitled Setting up your ASP.NET server (IIS).

If this doesn’t solve your problem and you are using .NET Framework 1.0, download and install .NET Framework 1.1 or .NET Framework 2.0.

Nathan Pakovskie is an esteemed senior developer and educator in the tech community, best known for his contributions to With a passion for coding and a knack for simplifying complex tech concepts, Nathan has authored several popular tutorials on C# programming, ranging from basic operations to advanced coding techniques. His articles, often characterized by clarity and precision, serve as invaluable resources for both novice and experienced programmers. Beyond his technical expertise, Nathan is an advocate for continuous learning and enjoys exploring emerging technologies in AI and software development. When he’s not coding or writing, Nathan engages in mentoring upcoming developers, emphasizing the importance of both technical skills and creative problem-solving in the ever-evolving world of technology. Specialties: C# Programming, Technical Writing, Software Development, AI Technologies, Educational Outreach

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