How to Use Windows Server IIS to Configure URL Rewrite Rules

If your company redesigns its website and changes the underlying technology from classic ASP (about.asp) to modern PHP or .NET Core (about-us), all of your old URLs will suddenly break. Anyone clicking a link from an old email, a Google search result, or a saved bookmark will hit a 404 Not Found error. This destroys your SEO rankings and frustrates users. To fix this on a Windows Server running Internet Information Services (IIS), you do not write complex code in your application; you intercept the traffic at the web server level using the URL Rewrite module.

What is URL Rewrite?

URL Rewrite acts like a bouncer at the front door of your web server. Before your actual website ever sees a visitor’s request, the module analyzes the URL they typed. If the URL matches a specific pattern (a Regular Expression), the module instantly changes the request and forwards it to the correct, modern page, completely invisibly to the user.

Step 1: Install the URL Rewrite Module

Unlike Apache (which has mod_rewrite built-in), Microsoft IIS does not include URL Rewrite natively. You must download it separately.

1. Open a browser on your Windows Server (or download it on your desktop and transfer it).
2. Search for “IIS URL Rewrite Module” and download the installer from the official Microsoft IIS.net website.
3. Run the installer. It requires no configuration, but you must close and reopen the IIS Manager console for the icon to appear.

Step 2: Create a Basic 301 Redirect Rule

The most common use case is forcing all traffic from HTTP to HTTPS, or forcing all traffic from domain.com to www.domain.com. We will configure a rule to redirect an old page to a new page.

1. Open Internet Information Services (IIS) Manager.
2. In the left pane, click on your specific website (e.g., “Default Web Site”).
3. In the middle pane, double-click the URL Rewrite icon.
4. In the right pane under Actions, click Add Rule(s)…
5. Choose Blank rule under the Inbound rules section and click OK.

Step 3: Configure the Pattern Matching

Now we define exactly what URL we are looking for.

• Name: Give it a descriptive name like “Redirect Old About Page”.
• Requested URL: Matches the Pattern
• Using: Regular Expressions
• Pattern: Type ^about\.asp$
  • Explanation: The ^ means the start of the string, the $ means the end. The \ escapes the period. This ensures it only matches exactly “about.asp” and not “about.asp/extra”.
• Ignore case: Keep this checked (Windows is usually case-insensitive, but web URLs can be tricky).

Step 4: Define the Action

Once IIS catches a user trying to access about.asp, what should it do?

1. Scroll down to the Action pane.
2. Action type: Change this from “Rewrite” to Redirect.
   • Rewrite changes the URL secretly on the server. The user’s browser still says about.asp, but they see the new content.
   • Redirect forces the user’s browser to physically load the new URL, updating the address bar and telling Google to update its search index.
3. Redirect URL: Type /about-us.
4. Redirect type: Select Permanent (301). This is critical for SEO.
5. Click Apply in the top-right Action pane.

Step 5: The web.config File

When you click Apply, IIS does not save this rule in a hidden Windows registry key. It actually writes raw XML directly into your website’s web.config file located in the root directory of your site (e.g., C:\inetpub\wwwroot\web.config).

If you open that file in Notepad, you will see a new <rewrite> block.

<rewrite>
    <rules>
        <rule name="Redirect Old About Page" stopProcessing="true">
            <match url="^about\.asp$" />
            <action type="Redirect" url="/about-us" redirectType="Permanent" />
        </rule>
    </rules>
</rewrite>

This is incredibly powerful because it means your rewrite rules are portable. If you migrate your website to a new Windows Server, simply copying the web.config file brings all your complex URL routing logic with it instantly.