SSL & Certificate Tools

Guides for SSL & Certificates

Background on what these tools check and how to read the results.

• How Let's Encrypt actually issues a certificateThe ACME protocol behind automated certificates: orders, challenges, key authorizations, CAA checks and rate limits.
• SNI: how one IP address serves hundreds of certificatesTLS must send a certificate before HTTP says which site was wanted. How SNI solves that, and why you sometimes get the wrong certificate.
• Mutual TLS explained: when both sides present a certificateHow mTLS differs from ordinary TLS, what the client certificate actually proves, how to issue and verify one.
• Self signed certificates: when they are fine and when they are notWhat a self signed certificate is, why browsers reject it, how to generate one properly with SANs.
• TLS 1.2 vs TLS 1.3: what changed and what you should disableHow TLS 1.3 cut the handshake to one round trip, removed every legacy cipher, what 0-RTT costs you, and which protocol versions to turn off today.
• Wildcard vs SAN certificates: which one should you buyWhat a wildcard certificate covers and what it does not, how SAN certificates differ, why one wildcard does not cover sub subdomains.
• HTTP vs HTTPS: what the S actually changesThe real differences between HTTP and HTTPS: what TLS encrypts and what it does not, ports 80 and 443, certificates, SEO impact.
• Convert SSL certificate formats: PEM, DER, PKCS#12, and PKCS#7What PEM, DER, PKCS#7, and PKCS#12 actually are, which servers expect which, and how to convert between them without mangling the key.