SSL Certificate Checker

// SSL Certificate Checker

Why SSL/TLS Certificates Matter

An SSL/TLS certificate encrypts the connection between your browser and a website, preventing anyone from intercepting or tampering with the data in transit. Without a valid certificate, sensitive information like passwords, credit card numbers, and personal data can be captured by attackers through man-in-the-middle (MITM) attacks.

Modern browsers show a padlock icon for sites with valid certificates and display security warnings for expired or missing certificates. Certificate authorities (CAs) like Let's Encrypt, DigiCert, and Sectigo verify domain ownership before issuing certificates. Let's Encrypt has made free, automated certificates available to everyone, making HTTPS the standard for all websites.

What to Check in an SSL Certificate

Verify the certificate hasn't expired, covers the correct domain(s) including subdomains via Subject Alternative Names (SANs), uses a modern protocol (TLS 1.2 or 1.3), and is issued by a trusted certificate authority. Certificates expiring within 30 days should be renewed immediately to avoid browser warnings.

FAQ

What is an SSL/TLS certificate?

An SSL/TLS certificate is a digital document that authenticates a website's identity and enables encrypted connections. It ensures data between your browser and the server can't be intercepted or modified by third parties.

What happens when a certificate expires?

Browsers will display a full-page security warning and may prevent users from accessing the site. Most users will leave immediately, causing lost traffic and revenue. Automated renewal with tools like Certbot prevents this.

Is TLS 1.2 still secure?

Yes, TLS 1.2 is still considered secure when configured properly. However, TLS 1.3 is preferred — it's faster (one fewer round-trip), removes outdated cipher suites, and provides better forward secrecy by default.

Are free certificates (Let's Encrypt) as secure as paid ones?

Yes. The encryption strength is identical. Paid certificates may offer extended validation (EV) which displays the organization name, warranty coverage, and dedicated support — but the cryptographic security is the same.