Determine whats wrong with your Azure Web / API App deployment

Sometimes a deployment goes wrong and instead of the actual app you get a message like this:

An error occurred while starting the application.
.NET Core 4.6.26020.03 X86 v4.0.0.0 | Microsoft.AspNetCore.Hosting version 2.0.1-rtm-125 | Microsoft Windows 10.0.14393 | Need help?

To see whats going wrong we have to enable logging:

  • Go to the Kudu environment (https://YOURSITE.scm.azurewebsites.net)
  • On the top menu, select Debug console -> PowerShell
  • Navigate to site -> wwwroot and open the web.config
  • Set the stdoutLogEnabled attribute to true and save the file. Example:
  • <?xml version="1.0" encoding="utf-8"?>
    <configuration>
    	<system.webServer>
    		<handlers>
    			<add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />
    		</handlers>
    		<aspNetCore processPath="dotnet" arguments=".\MyApp.dll" stdoutLogEnabled="true" stdoutLogFile=".\logs\stdout" />
    	</system.webServer>
    </configuration>
    
  • Create a folder named logs next to the web.config using mkdir logs

Now if you try to browse your site again, you should see a log file within the previously created directory containing additional information:

kudu