What is a wildcard SSL certificate?
A wildcard SSL certificate secures every first-level subdomain of a domain with a single certificate, written as *.example.com. It covers app.example.com and api.example.com, but not deep.sub.example.com. Hosting platforms use wildcards so every customer subdomain is served over HTTPS without issuing a certificate per site.
How does a wildcard certificate differ from a single-domain one?
A single-domain certificate names exactly the hostnames it covers. A wildcard covers every direct subdomain of one domain at once. That is convenient at platform scale and irrelevant for one site: if you host app.example.com and nothing else, a single-domain certificate is simpler and free from Let's Encrypt.
| Certificate | Covers | Does not cover |
|---|---|---|
example.com | The bare domain only | Any subdomain |
*.example.com | app, api, www and any other first level | example.com itself, or a.b.example.com |
| Multi-domain (SAN) | A named list of hostnames | Anything not on the list |
What does issuing a wildcard require?
DNS validation. A plain certificate can be validated by serving a file over HTTP, but a wildcard cannot: the certificate authority requires a TXT record on the domain, proving control of DNS itself. That is why wildcards need API access to your DNS provider and are harder to automate than a normal certificate.
Let's Encrypt certificates are valid for 90 days, so any certificate setup that is not automated will eventually expire and take the site down. Source: Let's Encrypt documentation
Do you need to buy one?
Usually not. Every InstaPods pod gets an HTTPS subdomain under a platform wildcard at no cost, and custom domains get their own certificate issued and renewed automatically. You would buy a wildcard only if you are running the platform yourself and issuing many subdomains under a domain you own.
Where wildcard ssl certificate shows up on InstaPods
Related terms
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