How long are SSL certificates valid?

Public certificates are currently capped at 398 days, and the industry is moving toward much shorter lifetimes. Let's Encrypt issues 90-day certificates on the assumption they are renewed automatically.

What happens when a certificate expires?

Browsers show a full-page warning that the connection is not private. Most visitors leave rather than click through, so an expired certificate effectively takes the site offline until it is renewed.

Why does my certificate work on www but not the bare domain?

Because the bare domain is not in the certificate's subject alternative names. A certificate for www.example.com does not automatically cover example.com — both need to be listed.

What is a self-signed certificate?

One signed by its own creator rather than a recognised certificate authority. It encrypts traffic but proves nothing about identity, so browsers reject it. Fine for local development, never for a public site.

AI & API Tools

SSL Certificate Checker

Inspects a domain's SSL/TLS certificate and reports its issuer, validity dates, days remaining, key algorithm and the alternative names it covers.

Free, no signupProcessed securely, never stored

Input

Domain

Result

Enter a domain to inspect its SSL certificate.

About

What the SSL Certificate Checker does

The expiry date is the field most worth watching. An expired certificate makes browsers show a full-page security warning that most visitors will not click past, and it happens regularly to sites where the renewal reminder went to someone who has since left. Checking days remaining takes seconds.

How it works

Using the SSL Certificate Checker

1Enter the domain name.
2A TLS connection is made and the certificate retrieved.
3Issuer, subject and validity dates are extracted.
4Days remaining until expiry are calculated.
5Subject alternative names and the cipher in use are reported.

Use cases

What people use it for

Checking how long before a certificate expires
Confirming a newly installed certificate is live
Verifying which hostnames a certificate covers
Diagnosing a browser security warning

FAQ

Frequently asked questions

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