If you want to run website builder domain under HTTPS protocol, you need to do the following steps:

1. Go to My Licenses page;
2. Click on the "Manage" button next to your Cloud brand;
3. "Add SSL";
4. Wait until the process is finished, and then website builder will start working with HTTPS protocol having a valid SSL certificate.

1. Open your On-Premises brand and change website builder domain by adding "https://" at the beginning of it (e.g., "builder.yourdomain.com" -> "https://builder.yourdomain.com");
2. Open file "config.json" in your website builder web root directory and update parameter "siteProApiUrl" by changing "http://" part to "https://";
3. Go to My Licenses page;
4. Click on the "Manage" button next to your On-Premises brand;
5. Click "Apply" button.