Proper method to remove www from address using IIS URL Rewrite

Question

What is the optimal way to remove the www subdomain from a url using IIS URL Rewrite?

Answer 1

If you want it to work with any hostname (not hardcoding it into the rule), you'd want to do something like this:

<rule name="Remove www" stopProcessing="true">
  <match url="(.*)" ignoreCase="true" />
  <conditions logicalGrouping="MatchAll">
    <add input="{HTTP_HOST}" pattern="^www\.(.+)$" />
  </conditions>
  <action type="Redirect" url="http://{C:1}/{R:0}" appendQueryString="true" redirectType="Permanent" />
</rule>

in the redirect action, the {C:1} contains the second capturing group in the condition, whereas the {R:0} contains whatever was in the rule (the path). appendQueryString="true" will also append any querystring to the redirect (if present). Keep in mind though, that any url hashes, if present, will be lost in the process since those don't get passed to the server.

Answer 2

IIS does it automatically for you:

Select site > URL rewrite > new rule > Canonical Host Name :)

Answer 3

The following one should work :

<system.webServer>
  <rewrite>
    <rules>
      <rule name="Remove WWW" stopProcessing="true">
        <match url="^(.*)$" />
        <conditions>
          <add input="{HTTP_HOST}" pattern="^(www\.)(.*)$" />
        </conditions>
        <action type="Redirect" url="http://www.example.com{PATH_INFO}" redirectType="Permanent" />
      </rule>
    </rules>
  </rewrite>
</system.webServer>

Answer 4

To do a redirect that will work for both http and https the following can be used

    <rewrite>
        <rules>
            <rule name="Lose the www" enabled="true" stopProcessing="true">
                <match url="(.*)" ignoreCase="true"/>
                <conditions logicalGrouping="MatchAll">
                    <add input="{HTTP_HOST}" pattern="^www\.(.*)$"/>                    
                </conditions>
                <action type="Redirect" redirectType="Permanent" url="{SchemeMap:{HTTPS}}://{C:1}/{R:1}" appendQueryString="true" />
            </rule>
        </rules>
        <rewriteMaps>
            <rewriteMap name="SchemeMap">
                <add key="on" value="https" />
                <add key="off" value="http" />
            </rewriteMap>
        </rewriteMaps>
    </rewrite>