SSL Certificate Checker

Instantly verify any website's SSL/TLS certificate. Check expiry dates, certificate chain, protocol strength, and more.

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Frequently Asked Questions

What does the SSL Certificate Checker do?

It connects to a website's server and retrieves detailed information about its SSL/TLS certificate, including validity status, expiry date, issuer, subject alternative names, cipher suite, and the full certificate chain.

How do I know if my SSL certificate is about to expire?

The tool displays the number of days remaining until your certificate expires. It color-codes the result: green for more than 30 days, yellow for 7–30 days, and red for fewer than 7 days or already expired.

What is a certificate chain and why does it matter?

A certificate chain (or chain of trust) links your website's certificate to a trusted root Certificate Authority (CA). If any link in the chain is missing or invalid, browsers will show a security warning to visitors.

What are Subject Alternative Names (SANs)?

SANs are additional domain names covered by a single SSL certificate. For example, a certificate for example.com might also include www.example.com and mail.example.com as SANs, so all three domains are secured.

Does this tool support checking any domain?

Yes, you can check any publicly accessible domain. Simply enter the domain name without the protocol (e.g., 'example.com' instead of 'https://example.com'). The tool connects on port 443 by default.

Complete Guide: How to Use the SSL Certificate Checker

Verify the SSL/TLS certificate for any domain with detailed analysis of the certificate chain, expiration date, issuer, key algorithm, and security configuration. Our tool checks for common SSL issues like expired certificates, weak ciphers, and chain problems that could cause browser warnings or security vulnerabilities.

Step-by-Step Instructions

1
Enter a domain name
Type the domain you want to check (e.g., example.com). No need to add https:// — the tool connects automatically.
2
Run the SSL check
Click Check to initiate the SSL/TLS handshake and retrieve the certificate. The check takes just a few seconds.
3
Review certificate details
See the issuer (CA), subject, validity period, days until expiry, key algorithm (RSA/ECDSA), key size, and serial number.
4
Check the certificate chain
Verify the full chain from leaf certificate through intermediates to the root CA. Chain issues are the most common SSL problem.

Common Use Cases

✓Monitoring — check certificate expiration dates before they cause outages
✓Troubleshooting — diagnose SSL errors and browser security warnings
✓Security audit — verify strong encryption algorithms and key lengths
✓Compliance — ensure certificates meet industry security requirements
✓Migration — verify SSL is correctly configured after server or hosting changes
✓Vendor management — check SSL status of third-party services your app depends on

Pro Tips

💡Set calendar reminders 30 days before certificate expiry. Better yet, use Let's Encrypt with auto-renewal.

💡Chain issues (missing intermediate certificates) cause errors on some devices but not others — always verify the full chain.

💡ECDSA certificates are faster than RSA and provide equivalent security with shorter keys (256-bit ECDSA ≈ 3072-bit RSA).

💡Check that your server supports TLS 1.2 and 1.3 — older versions (TLS 1.0, 1.1, SSL 3.0) are deprecated and insecure.

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