If you’ve ever encountered the "HTTP Error 500.30 - ASP.NET Core app failed to start" error with IIS, you know how frustrating it can be. This error can happen for a variety of reasons, and pinpointing the exact cause is crucial for resolving it quickly. This guide will walk you through some common causes and practical steps to solve this issue based on my personal experience and research from multiple sources. Trust me, getting your app back up and running doesn’t have to be an impossible task.

Understanding HTTP Error 500.30 in ASP.NET Core

Before we dive into the solutions, it’s important to understand what this error means. HTTP Error 500.30 indicates that your ASP.NET Core application failed to start on the server. This error usually occurs after deployment when using IIS to host the app. In most cases, the root cause is related to misconfigurations or missing dependencies, but there can be several other reasons as well. Now let’s dive into the solutions.

1. Check the Application Logs

Start by checking your application logs. Logs are your best friend when debugging issues in an ASP.NET Core app. You can find them in the Event Viewer under the "Application" section or in the logs directory of your app. Logs will give you specific error details, such as missing dependencies, invalid configurations, or even permission issues.

2. Verify the ASP.NET Core Version

Another common cause of the "HTTP Error 500.30" is a version mismatch. Your application might be targeting a specific version of ASP.NET Core, but that version is not installed on the server. 
An important point: Make sure to check the version of ASP.NET Core your application is using, and then install the corresponding version of the hosting bundle from Microsoft's site. For example, if your Core version is 8.0.8, you will need to install the same version of the hosting bundle on your server.
Link to download runtime & hosting bundle: https://dotnet.microsoft.com/en-us/download/dotnet

You can also try installing the full Hosting Bundle, .NET SDK, and runtime. I once encountered this issue in my staging environment, and nothing seemed to work,but after installing all three, it finally resolved the problem.


To check the installed version, you can run the following command in PowerShell: dotnet --info Ensure that the installed version on the server matches the version required by your application. If they don’t match, you’ll need to install the correct version from the .NET download page.

3. Verify IIS Configuration

Often, the problem lies in your IIS configuration. Ensure that the IIS Application Pool is configured to "No Managed Code". This setting is critical for hosting ASP.NET Core apps on IIS. Also, make sure that the correct hosting bundle is installed. You can download the ASP.NET Core Hosting Bundle from the Microsoft site, and it should match the runtime version your app is using.

4. Misconfigured Web.Config File

The web.config file is another common source of errors. If this file is misconfigured, IIS won't be able to properly start your ASP.NET Core application. Make sure that the paths in your web.config are correct, especially the one pointing to your dotnet.exe runtime.

5. Check Permissions

Another thing to consider is file and folder permissions. Ensure that the IIS worker process (usually iis_iusrs) has the necessary permissions to read and execute the files in your application’s folder. A simple way to test this is by temporarily giving full control to the IIS user and checking if the application starts correctly.

6. Diagnose with dotnet.exe

If you’re still stuck, try running the application manually using the dotnet.exe command. Navigate to the app’s directory and run: dotnet yourapp.dll This will provide more detailed error messages that can help you pinpoint what’s going wrong.

While the "HTTP Error 500.30 - ASP.NET Core app failed to start" can be frustrating, it’s not insurmountable. By following the steps outlined above—checking logs, verifying the correct version of .NET Core, fixing your IIS configuration, and adjusting permissions—you should be able to resolve the issue quickly and get your app back online. Always remember, fixing ASP.NET Core issues is a step-by-step process. Take it one step at a time, and you’ll be fine.

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