SSL Certificate Checker

The SSL Certificate Checker provides comprehensive details including certificate validity, expiration dates, issuer information, subject alternative names, signature algorithms, key sizes, certificate chains, security grades, and supported TLS protocols. This helps you understand the complete security posture of any website.

It's recommended to check SSL certificates regularly, especially 30-60 days before expiration. For critical websites, monthly checks are advisable. Many organizations set up automated monitoring to alert them when certificates are approaching expiration to prevent unexpected downtime.

The security grade (A+, A, B, C, D, F) evaluates the overall SSL/TLS configuration quality. It considers factors like certificate validity, protocol versions, cipher strength, and security best practices. A+ and A grades indicate excellent security, while lower grades suggest improvements are needed.

If your certificate is expiring within 30 days, contact your certificate provider or hosting service to renew it immediately. For Let's Encrypt certificates, ensure auto-renewal is configured. Always test the new certificate after installation to confirm proper functionality.

This tool can only check publicly accessible domains with valid DNS resolution. For internal domains, private networks, or localhost environments, you'll need to use local tools or access the certificate directly through your browser or SSL analysis software.

Subject Alternative Names are additional domains covered by a single SSL certificate. This allows one certificate to secure multiple domains (like www.example.com and example.com) or subdomains. Multi-domain and wildcard certificates commonly use SANs.

Yes, this tool only establishes a standard HTTPS connection to check certificate information, similar to what a web browser does. No sensitive data is transmitted, and the tool doesn't store any certificate information. It's the same as visiting your website in a browser.

A self-signed certificate is signed by the same entity that owns it, rather than a trusted Certificate Authority (CA). While self-signed certificates provide encryption, they don't provide identity verification and will trigger browser warnings. They're typically used for testing or internal use.

SSL checks can fail due to various reasons: domain not found, no SSL certificate installed, certificate expired, connection timeout, firewall blocking, or misconfigured SSL. The tool provides specific error messages to help identify the issue.

Modern websites should support TLS 1.2 and TLS 1.3 for optimal security. TLS 1.0 and 1.1 are deprecated and should be disabled. SSL 2.0 and 3.0 are completely insecure and must not be used. The tool shows which protocols your server supports.

To improve your SSL grade: use strong cipher suites, disable weak protocols (TLS 1.0/1.1), implement HSTS headers, ensure proper certificate chain configuration, use modern key algorithms, and keep your SSL/TLS implementation updated. Consider using tools like SSL Labs for detailed recommendations.

Certificate chain validation verifies that your SSL certificate is properly linked to a trusted root Certificate Authority through intermediate certificates. A complete chain ensures browsers can verify your certificate's authenticity. Missing intermediate certificates can cause SSL errors.