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IIS win-acme

ACME protocol can be used for Windows web servers and other services as well. Since certbot supports binding only to Apache and Ngnix servers, we will use another available tool win-acme - Windows ACMEv2 client, which enables to manage the certificates on IIS Windows web servers, Exchange servers or enables the use of custom scripts to automate certificate issuance and renewal in Windows server environments.

For more information about win-acme, refer to the win-acme documentation.


certbot can be used to manually manage certificates for Windows server. You need to create your own automation scripts in order to achieve automated binding with the IIS.


Before configuring win-acme with CZERTAINLY, you need to have the following:

  • win-acme installed in the host server. You can download the installation file from win-acme installation download section
  • Configured at least one RA Profile
  • Properly configured DNS records for the hostname you are trying to obtain the certificate for (for HTTP validation, the machine that win-acme is running on must have the correct common name configured in DNS)
  • If you intend to use automated detection of certificate common name, the IIS server needs to have at least configured hostname for one binding (port 80 for instance)
  • Access to HTTP or DNS resources on your IIS Web server, that will be used to validate ACME challenges
  • ACME protocol enabled according to the Enable ACME

For this guide, we will use http-01 challenge validation, but the dns-01 can be also configured and the process is similar.

Configuration of win-acme

win-acme client is designed to be primary used as ACMEv2 client for Let's Encrypt Certification Authority and other ACME compliant servers. Before the first use we need to configure win-amce client to connect to CZERTAINLY platform instead of Let's Encrypt CA that is the default server. To achieve this, we need to set up correct endpoints in win-acme configuration file settings.json. Edit the settings.json file located in the root of win-acme directory with your preferred text editor and change the following lines:


With these parameters, we are directly connecting to the already configured RA Profile with name czertainly that has ACME enabled. For more information follow win-acme settings.

win-acme Plugin support

win-acme supports various sources plugins for binding (IIS, Exchange etc.) and validation plugins to prove the identity (HTTP, WebDAV, DNS etc.). For details how to use them, please visit: win-acme source plugins and win-acme validation plugins.

Using win-acme with IIS and self-hosted HTTP challenge

Once each pre-requisite and configuration are set up, you can run win-acme executable file wascs.exe with administrator privileges (to enable automatic detection of IIS services) and follow these steps:

Interactive mode

  • Please choose from the menu: N (Create certificate, default settings)
  • Depending on your setup, we can either input the hostname of the certificate manually or detect it from the IIS configuration
  • If IIS bindings are configured correctly, you will be asked to point win-acme to the site you want to issue certificate for
  • In case your IIS bindings are not configured you will have to follow up with Full Options from the menu: M
  • When finalizing the selection of the certificate name win-acme will automatically use http-01 challenge. In this step win-acme will try to bind port 80 of the server and publish the challenge received from the ACME server; this challenge will be posted on the port 80 of your server
  • Upon successfully challenge validation, win-acme will create the HTTPS bindings in the IIS automatically

Make sure that the web server is reachable on the specified port number with the domain name you selected for the certificate from CZERTAINLY platform to validate the challenge. If the server is not accessible for the CZERTAINLY, it will not be able to validate the challenge and the process will fail.

Unattended mode

The following represents a sample process of issuing certificate for self-hosted IIS with binding to the host

wacs.exe `
--source iis `
--host `
--webroot C:\sites\wwwroot

For all win-acme command line arguments, refer to win-acme documentation.

Automation of certificate renewal

win-acme can automatically renew any certificate that it obtained from ACME server using Windows Scheduler task. To configure automated renewal, follow these steps:

Interactive mode

  • Run win-acme executable file wascs.exe with administrator privileges
  • Please choose from the menu: O (More Options)
  • Please choose from the menu> T ((Re)Create Scheduled Task)
  • Please specify the user you want the task to be run under (user with administrator privileges is recommended to allow automatic binding configuration on the IIS server)
  • The scheduled task for automatic renewal of all certificates managed by win-acme is now created

Unattended mode

wacs.exe `
Compatibility issues in older versions of Windows server

win-acme might have issues running properly on older versions of Windows Server (2012 and older) due to compatibility with TLS 1.2 cipher suite. If you are struggling to establish the connection with the ACME server, try to consult your SSL and TLS settings with administrators of your system.