Install Let's Encrypt SSL on Windows Server IIS | Free HTTPS Setup Guide
Ccentron Redaktion · September 2025·7 min read·Security, Tutorial
Securing web applications with HTTPS is crucial for protecting data in transit and ensuring user confidence. This guide shows how to install a free Let's Encrypt SSL/TLS certificate on Windows Server using Internet Information Services (IIS).
You’ll use the win-acme client to request and apply the certificate, bind it in IIS, and configure automatic HTTPS redirection. Optional instructions for Certbot and manual .pfx conversion are also included for advanced scenarios.
Install IIS
IIS is a built-in component of Windows Server that you can enable via Server Manager.
Open Server Manager from the Start menu.
Click Add Roles and Features.
Select Role-based or feature-based installation, then choose your server.
On the Server Roles screen, check Web Server (IIS).
Add any other required features, then click Install.
After installation, verify IIS by visiting your public server IP in a browser:
http://YOUR-SERVER-IP
You should see the default IIS welcome page.
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Create a Simple Web Application
To confirm IIS is serving content correctly, set up a basic HTML page:
Open File Explorer and create a folder for your site.
Select your server, then open Server Certificates.
Click Import, choose your .pfx file, enter the password, and confirm.
Navigate to Sites, select your domain, and click Bindings.
Click Add, select https, and configure:
Port: 443
Hostname: example.com
Certificate: Select from dropdown
Enable Require Server Name Indication
Click OK to apply the binding. Visit https://example.com to confirm the certificate is active.
Redirect HTTP Requests to HTTPS
Use the IIS URL Rewrite module to automatically redirect all HTTP traffic to HTTPS.
Install the URL Rewrite Module
Download the URL Rewrite module.
Run the installer and finish the setup.
Open IIS Manager, select your server, and verify that URL Rewrite appears in Features View.
Create a Redirect Rule in IIS
In IIS Manager, expand your server and select your website under Sites.
Double-click URL Rewrite.
In the Actions pane, click Add Rules.
Under Inbound Rules, select Blank rule and click OK.
Give the rule a name (e.g., Redirect to HTTPS).
Keep Requested URL as Matches the Pattern, using Regular Expressions.
Set the pattern to:
Code
(.*)
Uncheck Ignore case.
Add a Condition
Expand Conditions and click Add.
Set Condition input to:
{HTTPS}
Keep Check if input string as Matches the Pattern.
Set the pattern to:
Code
^OFF$
Click OK.
Define Redirect Action
Scroll to Action settings and configure:
Action type: Redirect
Redirect URL:
Code
https://{HTTP_HOST}{REQUEST_URI}
Uncheck Append query string
Set Redirect type to Permanent (301)
Click Apply in the Actions pane.
Test the Redirect
Open your browser and go to:
http://example.com
You should be redirected automatically to the HTTPS version.
If the redirect does not work, verify that a web.config file exists in your site root. If it’s missing, create one with the following content:
Code
<?xml version="1.0" encoding="UTF-8"?><configuration><system.webServer><rewrite><rules><rulename="Redirect to HTTPS"stopProcessing="true"><matchurl="(.*)"/><conditions><addinput="{HTTPS}"pattern="^OFF$"/></conditions><actiontype="Redirect"url="https://{HTTP_HOST}{REQUEST_URI}"appendQueryString="false"/></rule></rules></rewrite></system.webServer></configuration>
Save the file and test the redirect again in your browser.
Conclusion
In this tutorial, you learned how to secure a website hosted on Internet Information Services (IIS) with a free Let’s Encrypt SSL/TLS certificate on Windows Server. You configured IIS, created a basic web app, installed the certificate using either win-acme or Certbot, set up HTTPS bindings, and redirected HTTP traffic to HTTPS.
With SSL fully configured, your server is now ready for secure hosting. To extend this setup, you can install WordPress on IIS or use PHP Manager to run dynamic applications.
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