SSL Certificate Checker
Inspect the SSL/TLS certificate for any domain — view issuer, expiry date, SANs, and days remaining.
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How to use this calculator
- 1
Enter the domain name (without https://).
- 2
Click "Check Now" to connect to the server on port 443 and retrieve the SSL certificate.
- 3
Results show the issuer, validity period, days remaining, and Subject Alternative Names.
- 4
A certificate with fewer than 30 days remaining needs urgent renewal.
Frequently asked questions
What is an SSL/TLS certificate?
An SSL/TLS certificate is a digital document that authenticates a website's identity and enables encrypted HTTPS connections. It contains the domain name, certificate authority (CA) that issued it, and validity period. Browsers show a padlock icon when a valid certificate is present.
What are SANs (Subject Alternative Names)?
SANs are additional domain names covered by a single certificate. Modern certificates use SANs instead of wildcards for multi-domain coverage. For example, a SAN certificate might cover example.com and www.example.com and api.example.com in a single certificate.
My certificate is expiring — what should I do?
Renew it immediately if it expires within 30 days. If you use Let's Encrypt, certbot or your hosting provider should auto-renew. If you use a paid CA, generate a new CSR and submit a renewal request. Most CAs allow renewal 30–90 days before expiry.
What is the difference between DV, OV, and EV certificates?
DV (Domain Validation): proves you control the domain — issued in minutes, used by Let's Encrypt. OV (Organization Validation): also verifies your organization — takes 1–3 days. EV (Extended Validation): highest assurance, thorough vetting — takes days to weeks. DV is sufficient for most websites.
SSL Certificate Checker — Inspect any domain's TLS certificate
Why SSL/TLS matters
HTTPS encrypts data between the browser and server, preventing eavesdropping and tampering. Google uses HTTPS as a ranking signal. Browsers show "Not Secure" warnings for HTTP sites. Let's Encrypt made free DV certificates available in 2016, making HTTPS universal.
Certificate transparency
All publicly trusted certificates are logged in Certificate Transparency (CT) logs — public, append-only ledgers. This allows anyone to monitor what certificates have been issued for their domain. Tools like crt.sh let you search CT logs to detect unauthorized certificates.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →