Unable to start debugging on the web server. The remote server returned an error: (404) Not Found. Error when starting debug in Visual Studio

Question

I have set up project to be run on IIS for some time ago and when I did press F5 it did connect no problem. But recently this stopped working and I did get this error when I press F5 / press Debug->Start debugging:

Unable to start debugging on the web server. The remote server returned an error: (404) Not Found.

Here is my settings:

I am not sure what happened, probably some VS updates or Windows updates, but I've tried to google everywhere and nothing had worked. Attach to process works fine as before, but this simpler way stopped doing the trick.

Update:

Have tried Process Monitor to figure out what is going wrong and it looks like w3wp tries to access path MyProjectFolder\debugattach.aspx and the result is "NAME NOT FOUND". Don't know if this is the root of the problem though.

Solution 1

It appears that one of my colleagues has edited the web.config and added request filtering where he has removed the "DEBUG" verb. This disallowed debugging on F5. After adding it (or removing request filtering) everything works fine.

P.S. A lot of other possible problems with similar error is described here

Solution 2

In my case (Windows 10 & Visual Studio 2017) I had to install ASP.NET 3.5 and ASP.NET 4.7 under the Internet Information Services.

Click here to see the solution

Solution 3

Old post but I recently had this issue and making sure that the following settings were enabled in 'Programs and Features' (Windows 10) fixed the issue for me:

Solution 4

This happened to me because I was using the Rewrite module to redirect to https. I was running https://localhost/WebSiteName, but had put my machine name in the https binding in IIS Mgr, Default web Site, Bindings. When I removed the machine name it worked.

Solution 5

Recently I have faced the same issue in VS2013 Professional, instantly I get error 'Unable to start debugging on web server". I observed that whenever my current page is MVC view (.cshtml) file and I start debugging , the error window prompts every time. As switch the current document in my project to controller (.cs) file, and starts debugging, it works properly. So my workaround is to debug my code I have to be on (.cs) file not on (.cshtml / web.config) file. Hope that helps!

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