When is a wildcard certificate useful?

A wildcard certificate covers all subdomains of a domain in one go. That sounds like the obvious solution, but it is not always the best choice.

When it is worthwhile

If you create new subdomains regularly, or you have many of them. Every new subdomain then works securely straight away, with no extra step.

When it is not

With two or three fixed subdomains. Individual certificates are simpler then and often free through automatic issuance.

What it does not cover

More than one level. A wildcard on your domain does not cover a subdomain of a subdomain. That is the most common disappointment.

The security point

The same private key sits on every server that uses it. If one of them is compromised, all your subdomains are. A certificate per server limits the damage.

In practice

Choose a wildcard for convenience when the number of subdomains keeps changing, and separate certificates when your environments have different security levels.