What is the difference between SSL and TLS?

SSL is the predecessor to TLS. All certificates today use TLS 1.2 or TLS 1.3. TLS 1.0 and 1.1 are deprecated. TLS 1.3 is significantly faster and more secure than TLS 1.2.

What are Subject Alternative Names (SANs)?

SANs are additional domain names a single certificate covers, such as www.example.com and blog.example.com alongside example.com. Wildcard certificates cover all subdomains at one level.

How often should I check my SSL certificate?

Check 90, 30, and 7 days before expiry. An expired certificate causes all visitors to see a browser security warning, blocking traffic entirely.

What does a certificate name mismatch mean?

It means the server is serving a certificate whose Common Name or SANs do not include your domain. This causes browsers to display a security warning even if the certificate is otherwise valid.

What does certificate chain mean?

Your server certificate is signed by an intermediate CA, which is signed by a root CA. This chain must be complete. Missing intermediate certificates cause some browsers to reject the connection.

Does checking SSL here affect my certificate?

No. The checker performs a read-only TLS handshake, identical to what any browser does. Nothing is modified and your private key is never exposed.

What is the difference between SSL and TLS?

SSL is the predecessor to TLS. All certificates today use TLS 1.2 or TLS 1.3. TLS 1.0 and 1.1 are deprecated. TLS 1.3 is significantly faster and more secure than TLS 1.2.

What are Subject Alternative Names (SANs)?

SANs are additional domain names a single certificate covers, such as www.example.com and blog.example.com alongside example.com. Wildcard certificates cover all subdomains at one level.

How often should I check my SSL certificate?

Check 90, 30, and 7 days before expiry. An expired certificate causes all visitors to see a browser security warning, blocking traffic entirely.

What does a certificate name mismatch mean?

It means the server is serving a certificate whose Common Name or SANs do not include your domain. This causes browsers to display a security warning even if the certificate is otherwise valid.

What does certificate chain mean?

Your server certificate is signed by an intermediate CA, which is signed by a root CA. This chain must be complete. Missing intermediate certificates cause some browsers to reject the connection.

Does checking SSL here affect my certificate?

No. The checker performs a read-only TLS handshake, identical to what any browser does. Nothing is modified and your private key is never exposed.

SSL Checker

Verify SSL/TLS certificate validity, expiry date, issuer, protocol version and cipher suite for any domain.

What is an SSL Certificate?

An SSL/TLS certificate is a digital credential that authenticates a website's identity and enables an encrypted HTTPS connection. When a browser connects to a server, the certificate proves that the server is genuinely who it claims to be — preventing man-in-the-middle attacks. The data exchanged between the browser and server is then encrypted, protecting passwords, payment details, and personal information.

SSL certificates are issued by Certificate Authorities (CAs) — trusted organizations like Let's Encrypt, DigiCert, Sectigo, and GlobalSign. Each certificate contains the domain name, issuer details, validity period, public key, and a list of Subject Alternative Names (SANs) — additional domains the certificate covers, such as www.example.com alongside example.com.

For SEO, HTTPS is a confirmed Google ranking signal since 2014. Expired, misconfigured, or self-signed certificates trigger browser warnings that dramatically increase bounce rates and erode user trust. Google Search Console and Chrome DevTools flag certificate issues, but regularly checking expiry dates helps you act before problems arise.

When to Use the SSL Checker

Common use cases:

✓ Verify certificate expiry before it causes downtime
✓ Confirm a new certificate was installed correctly
✓ Audit client websites during SEO or security reviews
✓ Check that wildcard or SAN certificates cover all subdomains
✓ Verify TLS 1.2+ protocol for compliance requirements
✓ Diagnose HTTPS mixed content and redirect issues

What the security grade means:

A — TLS 1.3 or TLS 1.2 with strong cipher, valid certificate
B — TLS 1.2 with adequate cipher suite
C — Weak cipher (under 128-bit key strength)
F — Expired certificate or legacy TLS 1.0/1.1 protocol

SSL Checker

What is an SSL Certificate?

When to Use the SSL Checker

Common use cases:

What the security grade means:

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