An SSL (Secure Sockets Layer) or TLS (Transport Layer Security) certificate is a digital credential installed on a web server that establishes an encrypted connection between the server and the user’s browser. It verifies the website’s identity and ensures that data transmitted — including form submissions, login credentials, and payment information — cannot be intercepted. SSL certificates are indicated by the padlock icon in the browser address bar and the https:// prefix. They are a technical SEO requirement and a fundamental trust signal.