SSL Certificate Checker
Verify HTTPS connectivity, troubleshoot certificate issues, and inspect SSL/TLS configurations
HTTPS Connectivity Check
Enter a domain to verify that it's reachable over HTTPS. A successful connection means the server is serving a valid TLS certificate that your browser trusts.
OpenSSL Inspection Commands
Run these commands in your terminal for detailed certificate inspection. They use the domain entered above, or default to example.com.
Check certificate details
Connect to a server and display the full certificate chain
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -textCheck expiry dates
Show certificate valid from and valid to dates
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -datesCheck subject and issuer
Display the certificate subject (domain) and issuer (CA)
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -subject -issuerView certificate chain
Show all certificates in the chain from leaf to root
openssl s_client -showcerts -connect example.com:443 -servername example.com </dev/null 2>/dev/nullCheck Subject Alternative Names
List all domains covered by the certificate
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -ext subjectAltNameVerify certificate chain
Verify the full certificate chain against system trust store
openssl s_client -verify_return_error -connect example.com:443 -servername example.com </dev/null 2>&1 | head -20Certificate Types
SSL/TLS certificates come in three validation levels. The encryption is the same for all types - the difference is how thoroughly the Certificate Authority verifies the requester's identity.
Domain Validated
Blogs, personal sites, internal tools
Organization Validated
Business websites, SaaS apps
Extended Validation
Banks, government, e-commerce
How the Certificate Chain Works
Root Certificate Authority (CA)
Pre-installed in your browser/OS trust store. These are the ultimate trust anchors (e.g., DigiCert, Let's Encrypt ISRG Root).
Intermediate Certificate
Issued by the Root CA. Intermediate CAs sign your server's certificate. This adds a layer of security - if compromised, only the intermediate needs revoking.
Leaf (Server) Certificate
Your domain's certificate. Signed by the intermediate CA. This is what your server presents to clients during the TLS handshake.
Common SSL/TLS Issues
Click on an issue to see symptoms, causes, and step-by-step fixes.
Serve content over a global CDN?
Stack0 CDN handles SSL certificates, edge caching, and file delivery worldwide.
Get Started