What is SSL certificate expiry?
SSL certificate expiry is the date after which a site's TLS (SSL) certificate stops being valid. From then on, browsers warn visitors that the connection isn't secure.
In more detail
Certificates last weeks or months, not years: Let's Encrypt's last 90 days, and the industry keeps shortening the longest allowed lifetime. Most are renewed automatically, so expiry usually means automatic renewal quietly stopped working: a DNS change, a moved server, a firewall rule or an expired payment card.
When a certificate expires, most visitors see a full-page warning and leave, and some apps and APIs refuse to connect at all.
Worked example
A certificate expires on 30 November. OwlHound checks the expiry date every day and emails you when 14 days or fewer remain, so the first warning arrives on 16 November and repeats daily until the certificate is renewed.
See also
Related terms: Certificate chain and Downtime. Free tool: SSL checker. How OwlHound helps: SSL & domain expiry monitoring. All terms: monitoring glossary.
Frequently asked questions
What happens when an SSL certificate expires?
Browsers show a security warning instead of your site, and many visitors leave. Payment pages and API clients may stop working entirely.
How do I check when my certificate expires?
Open the padlock menu in your browser, or use our free SSL checker, which also checks the certificate chain.
Why did automatic renewal fail?
Usually because the renewal check can't reach the site any more: DNS moved, the server changed, a firewall blocks it, or the account that renews it lapsed.
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