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Remove IIS Server version HTTP Response Header

Jan Reilink

Remove HTTP response headers in Windows Server IIS 10 and ASP.NET

Windows Server IIS loves to tell the world that a website runs on IIS. It does so with the Server header in the HTTP response, as shown below. In this post I’ll show you how to remove response server headers in IIS. You don’t want to give hackers too much information about your servers, heh? ;-).

Normal HTTP Response headers

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Microsoft Internet Information Services

Even though I’m not a big fan of security by obscurity (are you?), removing common server response headers is often advised by security experts. Attackers might gain a lot of information about your server and network, just by looking at the response headers a web server returns.

Therefore it’s advised you remove at least some of these headers.

But let’s start with how a normal HTTP HEAD response looks like:

HTTP/1.1 200 OK
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Vary: Accept-Encoding
Server: Microsoft-IIS/8.0
X-UA-Compatible: IE=Edge,chrome=1
Date: Sun, 06 Jul 2014 10:05:34 GMT
Connection: close

Here you notice IIS displaying its version information in a Server header, as response:

Server: Microsoft-IIS/8.0

As with removing ETag headers in IIS, you can rewrite and empty the Server: HTTP response header in IIS with a URL Rewrite Module outboundRule.

Protip: looking to enable HTTP Strict-Transport-Security (HSTS) on IIS (or more HTTP security headers)?

Remove Server response header with an outboundRule URL Rewrite rule

Unfortunately you cannot really remove the Server header. But you can rewrite its content and empty it. On IIS 7+ (IIS 7, 8.5, 8.0, 8.5, IIS 10.0), use an rewrite outboundRule to remove the web server version information from the Server: header response.

Read this too:   Create your own CDN using IIS Outbound Rules

You can use the following URL Rewrite Outbound rule:

<rewrite>    
  <outboundRules rewriteBeforeCache="true">
    <rule name="Remove Server header">
      <match serverVariable="RESPONSE_Server" pattern=".+" />
      <action type="Rewrite" value="" />
    </rule>
  </outboundRules>
</rewrite>

What the outboundRule does is: it looks for the header – or serverVariable – Server: in the output response stream, and rewrites the value with an empty string (nothing).

The end result is an empty Server: response header line:

HTTP/1.1 200 OK
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Vary: Accept-Encoding
Server:
X-UA-Compatible: IE=Edge,chrome=1
Date: Sun, 06 Jul 2014 10:06:08 GMT
Connection: close

You’ve now successfully removed the Server version response from the HTTP headers!

This is a website-specific rule. If you want to create the rule for all of your applications, you have to create the rule at the server level. Also, some applications, especially third party applications, may require and depend on the Server header. Then you may need to remove this rule for those applications.

Rewrite ‘Server: Microsoft-IIS/8.0’ with your own server information – just for the fun

The fun part of rewriting response headers is that you can display your own information string. For example, if you give in an value in the Rewrite action, that message is displayed:

<action type="Rewrite" 
  value="Saotn Server Software systems, LTD." />
HTTP/1.1 200 OK
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Vary: Accept-Encoding
Server: Saotn Server Software systems, LTD.
X-UA-Compatible: IE=Edge,chrome=1
Date: Sun, 06 Jul 2014 11:19:16 GMT
Connection: close

Isn’t this fun, now is it? :)

Remove ASP.NET X-Powered-By header in IIS using web.config customHeaders

By default IIS tells the world it’s powered by ASP.NET, by placing an X-Powered-By header:

HTTP/1.1 200 OK
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Vary: Accept-Encoding
Server:
X-Powered-By: ASP.NET
X-UA-Compatible: IE=Edge,chrome=1
Date: Sun, 06 Jul 2014 10:07:37 GMT
Connection: close

This response header can be removed with a customHeaders setting in web.config, placed in the <system.webServer> node:

<httpProtocol>
  <customHeaders>
    <remove name="X-Powered-By" />
  </customHeaders>
</httpProtocol>

Now the X-Powered-By header is removed from the response header output

HTTP/1.1 200 OK
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Vary: Accept-Encoding
Server:
X-UA-Compatible: IE=Edge,chrome=1
Date: Sun, 06 Jul 2014 10:10:02 GMT
Connection: close

Protip: learn more about various HTTP security headers.

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X-AspNet-Version header

The X-AspNet-Version HTTP Header broadcasts to the world what version of ASP.NET is being used. Add the following content inside the <system.web> node in your application’s web.config file:

<httpRuntime
  enableVersionHeader="false" />

removeServerHeader requestFiltering in IIS 10.0

In IIS 10.0 (Windows Server 2016/2019), you can remove the Server header by configuring requestFiltering in your web.config system.webServer node:

<security>
  <requestFiltering removeServerHeader ="true" />
</security>

This way you don’t have to fiddle with complex outbound rewrite rules.

To remove ASP.NET’s X-Powered-By header you still need the customHeaders section as mentioned above.

52,265 views

45 comments

  1. Hi
    if i will send wrong request the server version is showing like below .

    HTTP/1.1 400 Bad Request
    Content-Type: text/html; charset=us-ascii
    Server: Microsoft-HTTPAPI/2.0
    Date: Mon, 27 Apr 2020 09:57:10 GMT
    Connection: close

    How to remove Server: Microsoft-HTTPAPI/2.0
    Content-Length: 334

    Reply

  2. Hi,
    We’re using URL Rewrite Outbound rule to clear the value of the Server header and it works when using GET or POST, but when we use HEAD method is would still show IIS 8.5.
    Any ideas why? The only difference I see is that we’re not using “rewriteBeforeCache=true”. Could that be the issue?

    Reply

    1. Hi Nikko,
      Thank you for your comment.

      At this moment I’m not sure whether the outbound rewrite rule triggers on a HEAD request. Unfortunately, I’m lacking the time to look it up.

      The HTTP/1.1 RFC states for HEAD requests:

      The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response. The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request.

      So it *should* produce the same output. But you could give https://forums.iis.net/ or https://stackoverflow.com/ a try for confirmation. I’m interested in the outcome.

      Reply

  5. Hello Jan,
    I am looking to implement this changes for my application which is running on windows server..
    Could you please help to share exact file name where I need to add above rewrite rule on window server
    reason why am asking as I have implemented same fix for removing server information for port 47001 and 5985 but this is something not working for 8080 port number. It was added in web.conf file and below is response message for 8080 port

    Reply

  7. Good day all, I am running into a problem: I succesfully created an Outbound Rule in IIS that rewrites the server header to “This is a Web Server” instead of Microsoft-IIS/7.5. However, after this the Active Directory Single Sign On is no longer working for the users. Is there another option that does not interfere with Single Sign On? It seems the server header is being used by Active Directory to authenticate. All ideas welcome!

    Reply

    1. Hi Marq! I’m sorry, but I wouldn’t know, I’m not familiar with Active Directory Single Sign On.

      Perhaps the renamed Server header doesn’t match the SPN anymore? You can verify SPN’s in your domain with setspn. And you can use tools like Chrome developer tools, fiddler, etc to view and inspect all header being sent and returned. (Edit: maybe you’ve renamed too many headers by accident?)

      Reply

  11. Hi,

    I am getting the Server Name as “Microsoft-IIS/8.5” even after rewriting the server name as “” in the Error pages. Following is the web.config code:

    Reply

    1. Hi Ankit,

      Unfortunately your web.config code got lost in the comment. But what do you mean with “in the Error pages”, like the default IIS error pages located in C:\inetpub\custerr\en-US? Or somewhere else? Perhaps you have to use existingResponse=passthrough too? See the other comments.

      Reply

      1. Hi Jan,

        I am redirecting the error to the custom error pages like

        and I am using the following to remove/rename the Server Name:

        But, then also Server Name is coming in the custom error pages. How to remove the server name from the custom error pages?

        Reply

          1. Hi Jan,

            Thanks for the advice. I hope this time my code is visible.

            I am developing a mobile friendly application using MEAN. So. my issue is that I want to remove/hide/rename the Server Name from all the pages. I am able to do so in all the pages except the custom error pages. I am redirecting the error to the custom error pages like:

            and I am using the following to remove/rename the Server Name:

            But, then also Server Name is coming in the custom error pages. How to remove the server name from the custom error pages?

          2. Hi Jan,

            Actually, the issue is that the server name is visible in the HTTP Headers. Using the outbound rule in web.config, the server name is removed from the web pages but it is not removed from the custom error pages to which I am redirecting. I have also used errorMode=”Custom” existingResponse=”PassThrough” but it’s still coming.

  12. When I used below code

    protected void Application_BeginRequest(object sender, EventArgs e)
    {
    var application = sender as HttpApplication;
    if (application != null && application.Context != null)
    {
    application.Context.Response.Headers.Remove(“Server”);
    }
    }
    Then I am getting following error.
    Error: This operation requires IIS integrated pipeline mode

    More Info: I am using IIS 10, website hosting as Application and Application pool as Classic mode. If I changed to Integrated mode then working fine. But right now I can not change to this on Production environment because it may create other issue.

    So, can you please suggest best solution in this situation.

    Reply

    1. Hi Rikin, thank you for your comment!

      I’m not a fan of Classic mode application pools. Why would you want to have IIS 6.0 behaviour? I’d say, fix the problems you have switching to Integrated mode, and move on from there turning off response headers. If Integrated mode is really not an option, try to use web.config settings to disable headers.

      HTH!

      Reply

  14. I also have a rule that redirects http requests to https. But the redirect sends back all headers, including the Server: header. This is the http rule:

    This is from the Microsoft URL Rewrite reference page:

    Usage of a Redirect action implies that no subsequent rules evaluated for the current URL after redirection is performed.

    Is there any way to remove the server header on a redirect?

    Reply

  15. I am using IIS 8.5 and whenever I attempt to use in my web.config IIS does not like it. I’ve seen that this only works on IIS7 or other versions. Is there a workaround or other method to remove the ASP version?

    Reply

  16. Removing the server variable from response using url rewrite outbound rules is not working . application is angular 4 application and My server is windows 8 with iis 8.5 and I have my web.config data as shown below .

    Reply

  18. Hi, great article, but I’ve got question/problem..

    At the first glance all seems be well, I receive modified http headers, but when I send request to doesn’t exists page (and server will return 404 webpage) server name is ‘IIS 8.5’ in the HTTP headers..

    I found what is a problem – custom error pages.

    When I remove httpErrors elements from web.config, Server Name header isn’t display in HTTP headers (in both cases – correct/incorrect webpage url).

    How can I fix it ? (I want to have custom error pages and remove Server Name header..)

    Regards
    AErot

    Reply

    1. Hi @disqus_E1570bwNoJ:disqus , thank you for your comment. Interesting… What are you using, PHP or ASP.NET, and which solution do you use to remove the Server: header? It might be a .NET Framework thingy.

      Reply

          1. Bullseye! It looks like it’s working with Passthrough :) I must think about error page in ASP.NET. Thx!

            Best
            AErot

          2. Nice find @disqus_E1570bwNoJ:disqus , if you have the relevant web.config lines for me (and the scripting language you use: ASP.NET, PHP or ASP), I can add it to this post. Thanks in advance!

          3. Hi,

            When i set the existingResponse=passthrough, the server information is not displayed for the 404 status code but my custom error pages defined in IIS stopped working. Is there any workaround for this?

  19. We have tried it. But it doen’t work. Probably because of this line (MVC…): routes.IgnoreRoute(“{resource}.axd/{*pathInfo}”);

    Reply

  21. I’ve a issue with the solution.
    I can do a request to /blalbla.axd (every name possible) and then the “Server” variable will have a value…

    Reply

  23. Is there any way to completely remove “Server: Microsoft-IIS/8.0” from a site having static pages only like ?

    Reply

    1. Hi Kunal, thank you for your comment.
      An IIS Outbound Rule rewrites the output stream (HTTP response), so it’ll also remove the Server header from static HTML files.

      Reply

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