SSL checker

Transport Layer Security (TLS/SSL) Certificate Audit

The SSL Certificate Checker initiates an outbound cryptographic TLS handshake with your target server on port 443. It inspects the remote server certificate chain to verify active validity periods, confirms the issuing Certificate Authority (CA), inspects Subject Alternative Names (SANs) for domain coverage, and identifies protocol versions. Regular certificate audits prevent unexpected service interruptions, browser security warnings, and search ranking downgrades caused by expired or misconfigured SSL certificates.

Worked Example: Production TLS Diagnostic

Conducting a diagnostic query against an active web host extracts operational security parameters:

Target Host: byoviral.com:443

Returned certificate telemetry breakdown:

• Common Name (CN): byoviral.com.
• Subject Alternative Names (SAN): byoviral.com, *.byoviral.com. The wildcard SAN guarantees that all first-level subdomains share legitimate cryptographic trust without triggering browser mismatch errors.
• Issuer Organization: Google Trust Services (WE1). A public certificate authority trusted by the major browser and operating system root stores.
• Key Type: A 256-bit ECDSA key, which keeps handshakes fast. Forward secrecy comes from the TLS 1.3 key exchange, not from the certificate itself.
• Lifecycle Status: Valid certificate with continuous countdown monitoring.

Common TLS Configuration Pitfalls

Web administrators frequently encounter several recurring SSL/TLS failure modes:

• Root certificate trust stores: An SSL certificate is only as trusted as the Certificate Authority that signed it. Certificates issued by self-signed authorities or private internal enterprise PKIs require explicit root installation on client operating systems to avoid hard security rejections.
• Missing intermediate certificate bundles: A web server must serve the leaf certificate along with intermediate CA certificates. While desktop browsers often cache known intermediates, mobile devices and automated API clients reject servers with missing intermediate chains with untrusted certificate errors.
• Hostname mismatch errors: If visitors navigate to www.domain.com but the server certificate only covers domain.com, modern browsers immediately abort navigation and display warning screens. Always verify that SAN attributes cover all public host variants.
• Silent automated renewal failures: Automated certificate renewal tools like Certbot or ACME clients can fail silently when firewall rules change, web server ports are modified, or challenge files are blocked by reverse proxies. Automated expiry monitoring catches renewal failures before certificates expire.
• Outdated protocol support: Supporting deprecated protocols like TLS 1.0 or TLS 1.1 exposes servers to downgrade attacks and fails PCI-DSS compliance audits. Production environments should enforce TLS 1.2 and TLS 1.3.

Related Server Infrastructure Tools

Confirm that your web server enforces strict HTTPS upgrades by scanning response headers with the HTTP Headers Checker. To inspect DNS CAA records that control which Certificate Authorities are authorized to issue certificates for your domain, use the DNS Lookup. To verify domain expiration dates alongside SSL validity, visit the WHOIS Lookup.