SSL/TLS certificates enable HTTPS encryption, protecting data in transit between browsers and servers. Understanding certificates helps you maintain secure websites and avoid common pitfalls.
What SSL Certificates Do
SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) encrypt data between clients and servers. Certificates prove the server's identity, preventing man-in-the-middle attacks. When you see the padlock icon in your browser, a valid certificate is in use. Without HTTPS, data travels in plain text—visible to anyone on the network.
Certificate Types: DV, OV, EV
Domain Validation (DV) certificates verify you control the domain—issued in minutes automatically. Organization Validation (OV) certificates verify business identity—takes days to issue. Extended Validation (EV) certificates require extensive vetting and show company name in browser (green bar in older browsers). All provide the same encryption strength; the difference is identity verification level.
Certificate Authorities
Certificate Authorities (CAs) issue and sign certificates. Browsers trust certificates signed by recognized CAs like DigiCert, Let's Encrypt, and Comodo. Self-signed certificates provide encryption but trigger browser warnings because they're not trusted by public CAs. Let's Encrypt provides free DV certificates, making HTTPS accessible to all.
Certificate Expiration
Certificates have validity periods—typically 90 days (Let's Encrypt) to 1 year (paid certificates). Expired certificates cause browser warnings and can break site access entirely. Automated renewal (via certbot or similar) prevents expiration surprises. Monitoring certificate expiration is critical for production systems.