An SSL/TLS certificate is a digital certificate that authenticates a website's identity and enables encrypted communication between a visitor's browser and the web server. The "S" in HTTPS stands for "Secure" — and SSL certificates are what make HTTPS possible.
SSL certificates contain the domain name they're issued for, the certificate authority (CA) that issued it, the validity period (issue and expiry dates), the public key used for encryption, and the digital signature from the CA. Modern certificates use TLS (Transport Layer Security), though the term "SSL" is still commonly used.
Our SSL checker verifies that your certificate is valid and trusted, checks the expiry date and days remaining, inspects the certificate chain for intermediate CA issues, identifies the issuing CA, detects self-signed certificates, and checks for wildcard coverage and Subject Alternative Names (SANs).
Expired or misconfigured SSL certificates cause browser security warnings that drive users away, harm SEO rankings, and break HTTPS connections. Regular SSL monitoring is critical for any production website, e-commerce platform, or API endpoint. Most CAs issue certificates valid for 90 days (Let's Encrypt) to 1 year (commercial CAs) — set reminders to renew before expiry.