A simple ACMEv2 client for Windows (for use with Let's Encrypt et al.)

Getting started


  • Download the latest version of the program from this website. For most users the file called is recommended, but if you want to run on a 32 bit system you should get the x86 version instead of the x64 one, or if you want to download or develop extra plugins, you should get the pluggable version instead of the trimmed one.
  • Unzip files to a non-temporary folder, so that the scheduled task will be able to run. We recommend using %programfiles%\win-acme.
  • Run wacs.exe (this requires administrator privileges).
  • Follow the instructions on the screen to configure your first renewal.

Creating your first certificate

Note: the default settings are for users looking to install a regular (non-wildcard) certificate on their local IIS instance. For any other scenario you should skip straight to the section on advanced use.

  • Choose N in the main menu to create a new certificate with default settings.
  • Choose how you want to determine the domain name(s) that you want to include in the certificate. This can be derived from the bindings of an IIS site, or you can input them manually.
  • A registration is created with the ACME server, if no existing one can be found. You will be asked to agree to its terms of service and to provide an email address that the administrators can use to contact you.
  • The program negotiates with ACME server to try and prove your ownership of the domain(s) that you want to create the certificate for. By default the http validation mode is picked, handled by our self-hosting plugin. Getting validation right is often the most tricky part of getting an ACME certificate. If there are problems please check out some common issues.
  • After the proof has been provided, the program gets the new certificate from the ACME server and updates or creates IIS bindings as required, according to the logic documented here.
  • The program remembers all choices that you made while creating the certificate and applies them for each subsequent renewal.