A wildcard certificate covers a domain and its subdomains at one level, written with an asterisk, such as *.example.com. One certificate can then secure many names.
A certificate for *.example.com covers names like www.example.com, mail.example.com and shop.example.com, without listing each one. A new subdomain is covered at once, without issuing a new certificate.
It does not cover names one level deeper, such as a.b.example.com. The bare domain example.com usually has to be listed in the certificate as well.
Wildcards are common when a site has many subdomains or when new ones are added often. Automated issuance typically asks for proof through a DNS record.
The same key protects every name it covers, so it needs careful handling. Its end date applies to all names at once. For a single name, a normal certificate is often enough.
SSL Domain Detective shows when each of your certificates ends, wildcard or not. Open SSL Domain Detective
SSL Domain Detective is now available on the App Store.
Last reviewed: 2026-11-02
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