Article ID: 247404 - Last Review: December 3, 2007 - Revision: 2.6

How to Modify the Cache-Control HTTP Header When You Use IIS

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SUMMARY

Web administrators who use Internet Information Services (IIS) may need to periodically disable the caching of content that changes frequently. This article describes how to set the value of the Cache-Control HTTP Header by using Active Server Pages (ASP), as well as the metabase property CacheControlCustom.

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MORE INFORMATION

When you work with content that often changes, you may want to specify what content can be cached and what cannot, and if the client or a proxy server should cache the content. You can specify these options in IIS through the CacheControlCustom property, which can be set for the entire server, a particular Web site, or a specific physical or virtual directory. Setting this property returns HTTP headers that resemble the following:

HTTP/1.1 200 OK
Server: Microsoft-IIS/5.0
Cache-Control: <CACHE SETTING>
Content-Type: <type>/<subtype>
Content-Length: <size of content>

The cache setting value is determined by the HTTP/1.1 specification.

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Commonly-Used HTTP/1.1 Cache-Control Header Values

The HTTP/1.1 specification in RFC 2616 defines several values for the Cache-Control header. The following list contains a few of the more common values that are used.

Public: The HTTP response may be cached by any cache. For example, either a client or a proxy server can cache the response. This allows sharing of content across users who are using the same proxy server.
Private: The response message is intended for a single client and must not be cached by a shared cache. For example, a proxy server should not cache the response even though a client can. This allows the client to maintain a cached version, while other clients that are using the same proxy server maintain different cached versions.
No-cache: No cache in the entire path should maintain a cached copy of the response. This allows you to specify that neither the client or proxy server will respond to a subsequent content request by using a cached version.

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Setting the Cache-Control Property

The following examples define different methods for setting this value:

For a Page

Using Active Server Pages (ASP), the following ASP code disables caching of a particular page:

<% @Language="VBScript" %>
<% Response.CacheControl = "no-cache" %>

NOTE: This code must be inserted at the beginning of the page, unless buffering is enabled, because it is modifying the HTTP headers.

For a Folder

The following examples set the Cache-Control setting for a folder or virtual directory named "Images" in the default Web site:

Using Adsutil.vbs:
1. Open a command prompt and change to your C:\InetPub\AdminScripts folder.
2. Run the following command:
  CSCRIPT ADSUTIL.VBS SET W3SVC/1/ROOT/images/CacheControlCustom "no-cache"
Using ADSI Scripting:
2. In Notepad, enter the following ADSI code:
  Option Explicit Dim objCache Set objCache = GetObject("IIS://localhost/w3svc/1/root/images") objCache.CacheControlCustom = "no-cache" objCache.SetInfo
3. Save the file as Disablefolder.vbs in your C:\InetPub\AdminScripts folder, and then close Notepad.
4. At a command prompt, change to your C:\InetPub\AdminScripts folder.
5. Run the following command:
  CSCRIPT DISABLEFOLDER.VBS