Guides 4 min read
SSL Certificate Monitoring: Never Miss a Renewal Again
An expired SSL certificate turns your site into a browser warning. Why certificates still expire with auto-renewal, what to monitor and how to set reminders that work.
ReadGlossary · Domains, DNS, email and certificates
What is SSL certificate expiry?
SSL/TLS certificate expiry is the date after which a website’s certificate is no longer valid. From then on, browsers show a security warning instead of the site, and API clients refuse to connect.
How it works and why it matters
A certificate binds a domain name to a public key and is signed by a certificate authority. Each one is valid between two dates, notBefore and notAfter, in the X.509 format of RFC 5280. “SSL certificate” is the old name; today’s connections use TLS (RFC 8446 for TLS 1.3).
Lifetimes are getting shorter. Since March 15, 2026, publicly trusted certificates may be valid for at most 200 days, falling to 100 days in March 2027 and 47 days in March 2029, by decision of the CA/Browser Forum. Let’s Encrypt certificates last 90 days. Short lives make automatic renewal essential.
Automatic renewal still fails: a changed DNS record breaks validation, a firewall blocks the challenge, the server isn’t reloaded after renewal, or a certificate on a load balancer is handled by hand. Watching the expiry date of the certificate actually served tells you when renewal didn’t happen.
How Uptimecheck helps
Every HTTPS check in Uptimecheck reads the certificate the server actually presents. You get reminders 30, 14, 7 and 1 day before it expires, and on the day, and an invalid certificate fails the check unless you turn certificate verification off for that monitor.
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Read more in the guides
Guides 7 min read
SSL Certificate Errors Explained: Causes and Fixes
NET::ERR_CERT_DATE_INVALID, ERR_CERT_COMMON_NAME_INVALID and the other browser SSL warnings explained: what each one means, what causes it and how to fix it on your server.
ReadQuestions
What happens when an SSL certificate expires?
Browsers show a full-page warning such as NET::ERR_CERT_DATE_INVALID, most visitors leave, and apps and APIs that verify certificates stop connecting. The server keeps running, so server monitoring alone won’t notice.
How long is an SSL certificate valid?
Since March 15, 2026, at most 200 days for publicly trusted certificates; from March 2027 at most 100 days, and from March 2029 at most 47. Let’s Encrypt certificates last 90 days.
If renewal is automatic, why watch the expiry date?
Because renewal fails silently. A reminder 14 days before expiry, on a certificate that should have renewed 30 days before, is your sign that the automation broke.
Downtime is obsolete.
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