HTTP Error 500.31 - Failed to load ASP.NET Core runtime

Imagine you're a web developer, excited to launch your brand new ASP.NET Core application, and you are met with the dreaded “HTTP Error 500.31 - Failed to load ASP.NET Core runtime”. Panic sets in, and you start wondering what went wrong. But fear not! Here we will break down this error for beginners and provide you with clear insights into its causes, precautions, diagnosis, and most importantly, solutions.

HTTP Error 500.31 - Failed to load ASP.NET Core runtime

HTTP Error 500.31 is a status code that signifies an internal server error. More specifically, it indicates that the ASP.NET Core runtime required to run your application has failed to load. This runtime powers ASP.NET Core web applications and services, so a failure to load it prevents the application from running properly. In simpler terms, your web server can't find or initialize the necessary framework to execute your web application. This can be a frustrating roadblock, but with right knowledge and approach, you can overcome it.

Causes of HTTP Error 500.31 - Failed to Load ASP.NET Core Runtime

To address this issue, we first need to understand what might have caused it in the first place. Several factors could be contributing to this error:

Missing or Incorrect .NET Runtime

ASP.NET Core applications depend on having the correct version of the ASP.NET Core shared framework installed on the server. If the required version is not present, you'll get the HTTP Error 500.31. For example, an application built with ASP.NET Core 3.1 needs the corresponding 3.1 runtime installed. If only .NET Core 2.2 is available, it won't work.

Missing Dependencies

The ASP.NET Core runtime depends on other libraries like Visual C++ Redistributable for Visual Studio. If any of these dependencies are missing or the wrong version is installed, the runtime itself may fail to load correctly.

Incomplete Deployment

If the deployment of your application was not carried out properly, it might result in this “Error 500.31 - Failed to Load ASP.NET Core Runtime“. Ensure all necessary files and dependencies are deployed correctly.

Insufficient Permissions

To start properly, the ASP.NET Core runtime needs to read/execute permissions on certain files and folders, like wwwroot. If the permissions are incorrect, perhaps due to a misconfiguration, the runtime will fail to initialize.

Corrupted Runtime Installation

An ASP.NET Core runtime installation can get corrupted over time or during an update. This can lead to the “HTTP Error 500.31 - Failed to Load ASP.NET Core Runtime“.

Hosting Issues

When hosting ASP.NET Core in IIS, the app pool needs to be configured correctly to load the runtime. Improper settings like incorrect bitness or an unsupported .NET CLR version will lead to HTTP Error 500.31.

Incorrect Runtime Bitness

The ASP.NET Core runtime comes in 32-bit and 64-bit variants. If the application targets one bitness but the installed runtime is the other, they won't be compatible. For instance, a 32-bit application expecting the 32-bit runtime will fail if only the 64-bit runtime is installed.

Precautions Before Troubleshooting HTTP Error 500.31 - Failed to load ASP.NET Core runtime

Before you start troubleshooting the “HTTP Error 500.31 - Failed to Load ASP.NET Core Runtime“, there are a few preparatory steps worth taking:

  • Backup Your Application: Make sure to create backups of your application and configurations before making any changes. This is your safety net in case things go wrong.
  • Double-check .NET Versions: Ensure that your application and server are both using the same version of .NET. This small step can save you from hours of troubleshooting.
  • Review Configuration Files: Double-check your configuration files like web.config, appsettings.json, and launchSettings.json to verify that they are correctly set up.
  • Validate Permissions: Confirm that your application and its components have the necessary permissions to access files, directories, and the ASP.NET Core runtime.
  • ASP.NET Application start: Make sure the application starts correctly in your development environment. Errors happening only on the production server are often environmental.
  • Check Logs: Check the application logs for additional error information. Detailed error messages can help pinpoint causes.

Taking these precautions upfront will give you a better starting point for diagnosing the “HTTP Error 500.31 - Failed to Load ASP.NET Core Runtime“ problem.

Diagnosing HTTP Error 500.31 - Failed to load ASP.NET Core runtime

Diagnosing the root cause of HTTP Error 500.31 is an important step in resolving it effectively. Here is how you can approach this:

  • Check Server Logs: Start by examining server logs for error messages or clues about what went wrong. These logs are your best friend when it comes to troubleshooting.
  • .NET CLI: If you have access to the server, you can use the .NET CLI to check the installed .NET runtimes. Running commands like dotnet --list-runtimes can help you identify any missing runtimes.
  • Application Logs: Check your application's logs for any errors or exceptions. These logs can provide valuable insights into what's causing the “HTTP Error 500.31 - Failed to Load ASP.NET Core Runtime“.
  • Test on a Local Environment: If possible, replicate the error on a local development environment. This can help you pinpoint if the HTTP Error 500.31 issue is specific to the server or your application code.

Solutions for HTTP Error 500.31 - Failed to load ASP.NET Core runtime

Now, let's look into the heart of the matter, how to resolve “HTTP Error 500.31 - Failed to load ASP.NET Core runtime”. Here are some solutions that can help you get your ASP.NET Core application back on track:

Solution 1: Install the Required .NET Runtime OR ASP.NET Hosting Bundle

If the server is missing the necessary .NET runtime or ASP.NET Hosting Bundle, you must install it. You can download and install the .NET runtime and ASP.NET Hosting Bundle from the official .NET website.

Solution 2: Update .NET Versions

Ensure both your application and server are using the same .NET versions. If they don't match, update your application to the correct version.

Solution 3: Check Configuration Files

Review your configuration files and make sure they are correctly set up. Pay close attention to connection strings and paths to the ASP.NET Core runtime.

Solution 4: Redeploy Your Application

If you suspect an incomplete deployment, try redeploying your application. Be thorough and ensure all files and dependencies are included.

Solution 5: Permissions Check

Verify the permissions for your application. The user running the web server (often IIS_IUSRS on Windows) must have read and execute permissions on the necessary directories.

Solution 6: Reinstall .NET Runtime

If you suspect a corrupted .NET runtime, uninstall and then reinstall it. This can help resolve “HTTP Error 500.31 - Failed to load ASP.NET Core runtime” or any issues related to runtime corruption.

Solution 7: Check for Windows Updates

If you're running your application on Windows, ensure that your server has the latest updates installed. Some runtime issues can be resolved by updating the operating system.

Solution 8: Switch to the Correct Bitness

If bitness is the issue, you have two options:

Reinstall the .NET runtime in the required bitness (32-bit or 64-bit)

Alternatively, recompile the application for the installed bitness.

Solution 9: Consult the Community

Don't hesitate to seek help from the developer community. Platforms like Stack Overflow and forums dedicated to ASP.NET Core can be valuable sources of assistance.

Solution 10: Contact Hosting Provider

If your application is hosted on a third-party server, reach out to your hosting provider's support team. They might have specific solutions or insights for their environment.


“HTTP Error 500.31 - Failed to load ASP.NET Core runtime” can be a daunting obstacle for beginners and experienced developers alike. However, armed with a better understanding of its causes, precautions, diagnosis, and solutions, you can tackle it with confidence.

Remember to take precautions by backing up your application and ensuring version compatibility. When diagnosing the issue, consult server logs, use the .NET CLI, and review application logs. With these insights in hand, you can work towards a solution that matches the specific cause of the “HTTP Error 500.31 - Failed to load ASP.NET Core runtime”.

Be patient, stay persistent, and don't hesitate to seek help when needed. Troubleshooting HTTP Error 500.31 is a part of the development journey, and as you gain experience, you'll become more adept at tackling such challenges. Ultimately, resolving this error will not only get your ASP.NET Core application back on track but also deepen your knowledge and expertise in web development.