Create a self-signed certificate in macOS Server
If your server doesn’t have an SSL certificate, or if you need another one, start by creating a self-signed certificate.
Create a self-signed certificate
- In the sidebar of the Server app  , select Certificates. , select Certificates.
- Click the More button  and choose Show All Certificates. and choose Show All Certificates.
- Click the Add button  , then choose Create a Certificate Identity from the pop-up menu. , then choose Create a Certificate Identity from the pop-up menu.
- In the Name field of the Certificate Assistant, enter your server’s fully qualified host name (for example, server.example.com). - Leave the other settings unchanged. Identity Type should be Self Signed Root, Certificate Type should be SSL Server, and “Let me override defaults” should be deselected. 
- Click Create, then click Continue when prompted. 
You can choose the new self-signed certificate for the server. For information, see Use an SSL certificate in macOS Server.
You can also use the new self-signed certificate to request a signed certificate from a Certificate Authority. For instructions, see Obtain a trusted certificate in macOS Server.
Configure clients to trust a self-signed certificate
Clients need to be told to trust the self-signed certificate.
- If you’re using a self-signed certificate with your server, you can prepopulate your Mac clients with the certificate by adding it to a configuration profile and then sending that profile to the Mac clients. For more information on how to create configuration profiles, see Work with configuration profiles in macOS Server.