Run the handshake diagnostic calculator above.
About this tool
SSL (Secure Sockets Layer) configurations establish encrypted channels between browsers and servers using asymmetric cryptography handshakes.
Asymmetric RSA Encryption Formula
Asymmetric keys encrypt communications by processing data arrays through large prime modular exponentiations:
Where:
- C is the cipher text payload.
- M is the decrypted message.
- e, n represent the public key coordinates.
Our local PEM parser processes base64 certificate text directly on your device, ensuring maximum security when analyzing raw certificate files.
Frequently asked questions
Everything you need to know about SSL Certificate Checker.
What does an SSL certificate check verify?
The checker verifies: whether a valid SSL/TLS certificate is installed, the certificate's expiry date, the issuing Certificate Authority (CA), the full certificate chain (root → intermediates → leaf), Subject Alternative Names (SANs) covered, and whether the certificate matches the domain name queried.
What is a certificate chain and why does it matter?
A certificate chain links your server's certificate to a trusted root CA through one or more intermediate certificates. If an intermediate is missing, browsers like Chrome and Firefox will show a 'certificate not trusted' error even if your certificate itself is valid. The checker displays the full chain so you can identify gaps.
What is the difference between DV, OV, and EV SSL certificates?
DV (Domain Validated) only confirms you control the domain — issued in minutes, commonly free (Let's Encrypt). OV (Organisation Validated) verifies the legal organisation behind the domain — takes 1–3 days. EV (Extended Validation) includes the strictest vetting and used to show the company name in the browser bar, though most browsers have moved away from displaying this visually.
How far in advance should I renew my SSL certificate?
Best practice is to renew at least 30 days before expiry. Automated systems (like Certbot/Let's Encrypt) typically renew at 60 days remaining. Browser trust stores begin showing warnings to users within days of expiry, which can dramatically impact conversion rates.
Why does the checker show my certificate as expired even though I just renewed it?
This is usually a caching issue. Your server may still be serving the old certificate from memory without a restart, or a CDN/load balancer in front of your server holds a cached copy. Restart your web server (nginx/Apache) and flush your CDN cache after renewing.