SSL/TLS
The cryptographic protocols that encrypt data in transit between a browser and a server, shown as the padlock in your address bar.
Definition
SSL (Secure Sockets Layer) and its modern successor TLS (Transport Layer Security) are cryptographic protocols that establish an encrypted connection between a client (usually a browser) and a server. This ensures that data transmitted – passwords, credit card numbers, personal information – cannot be read or tampered with by a third party.
Why it matters
Without encryption, data travels across the internet in plain text, readable by anyone who can intercept it. TLS makes eavesdropping and man-in-the-middle attacks computationally infeasible. It’s also a trust signal: browsers mark non-HTTPS sites as “Not Secure,” and Google uses HTTPS as a ranking factor.
Example
The padlock icon in your browser’s address bar indicates an active TLS connection. When you submit a login form on an HTTPS site, your credentials are encrypted before leaving your device. Services like Let’s Encrypt provide free TLS certificates, making HTTPS accessible to everyone.