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The SSL Certificate Expiry Calculator computes days remaining until an SSL/TLS certificate expires, identifies urgent renewal needs, and calculates renewal reminder dates based on your preferred lead time (default 30 days). SSL/TLS certificates secure HTTPS connections by encrypting data and verifying server identity. Expired certificates cause browser security warnings, broken HTTPS, and erode user trust — making expiry tracking essential for any site or API.
Formula
- exp
- Expiry Date (date) — Certificate notAfter timestamp
- iss
- Issued Date (date) — Certificate notBefore timestamp
Guida passo passo
- 1Enter the certificate expiration date (visible in browser by clicking the padlock icon)
- 2Optionally enter the issued date for total validity period and percent-of-life-used calculation
- 3Set your reminder lead time in days (30 default; some teams use 14 or 60)
- 4Calculator computes days until expiry and renewal reminder date
- 5Status: HEALTHY (>30 days), RENEW SOON (within reminder threshold), URGENT (<7 days), EXPIRED (negative days)
- 6Pull total certificate validity from issued + expiry dates if both provided
- 7Visual bar compares days left to your reminder threshold
Esempi risolti
Errori comuni da evitare
- ✕Manually tracking expiration without automated alerts — most outages from expired certs happen because nobody was watching
- ✕Ignoring intermediate certificates — full chain must be valid, not just the leaf cert
- ✕Not testing renewal in advance — Let's Encrypt renewals can fail silently due to ACME challenge issues
- ✕Forgetting wildcard cert renewals affect all subdomains simultaneously
Domande frequenti
How long are SSL certificates valid?
Public CA certificates max 397 days (since Sep 2020). Let's Encrypt issues 90-day certs. Internal CAs can issue longer (some 10+ years). Browser enforced limits prevent certs over 398 days from being trusted.
What happens when a cert expires?
Browsers show security warnings (NET::ERR_CERT_DATE_INVALID), block connections, and damage SEO. API clients reject the connection unless they disable verification (security risk).
Should I automate renewal?
Yes — use certbot/acme.sh for Let's Encrypt, or your cloud provider's certificate manager (AWS ACM, Azure App Service Certificates). Manual renewal is the #1 cause of expiration outages.
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