IIS 8 URL Rewrite Module for redirecting Non-WWW to WWW (except URLs with sub-domains)

Question

I am redirecting all my websites non-www versions of domains to www version.

However, the side-effect is that it is also redirecting sub-domains with www

e.g. api.example.com to www.api.example.com

Which is not what I wanted. I need all the sites with sub-domains to NOT prepend the www.

Here are my current rules:

<system.webServer>
    <rewrite>
        <globalRules>
            <clear />
            <rule name="non-www to www" enabled="true" stopProcessing="false">
                <match url=".*" />
                <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
                    <add input="{CACHE_URL}" pattern="^(.+)://(?!www)(.*)" />
                </conditions>
                <action type="Redirect" url="{C:1}://www.{C:2}" />
            </rule>     

            <rule name="http to https" stopProcessing="true">
                <match url="(.*)" /> <!-- Require SSL must be OFF in the site settings -->
                <conditions>
                <add input="{HTTPS}" pattern="off" ignoreCase="true" />
                </conditions>
                <action type="Redirect" redirectType="Found" url="https://{HTTP_HOST}{REQUEST_URI}" />
            </rule>
        </globalRules>
    </rewrite>
</system.webServer>

Is it possible to make a rule that only redirects to www.example.com if the input doesn't start with 'www' AND it's NOT a sub-domain?

Anything with a sub-domains must not prepend the www

Please help as I'm already trying last two days without success.

Thank you in advance!!

Answer 1

You need to change your regexp to:^[^.]*\.[^.]{2,3}(?:\.[^.]{2,3})?$ and this regexp will catch only second-level domains.

I took it from this answer: https://stackoverflow.com/a/21174423/1954204

At the end your rule will be like that:

<rule name="non-www to www and https" enabled="true" stopProcessing="false">
    <match url=".*" />
    <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
        <add input="{HTTP_HOST}" pattern="^[^.]*\.[^.]{2,3}(?:\.[^.]{2,3})?$" />
    </conditions>
    <action type="Redirect" url="https://www.{HTTP_HOST}" />
</rule>