TLS, or Transport Layer Security, is a cryptographic protocol that secures communication between applications over a network, most commonly between a web browser and a web server. Its primary purpose is to ensure that data exchanged over the internet remains private, authentic, and unaltered while in transit.
In practical terms, TLS is what makes HTTPS possible. When you visit a website using HTTPS, TLS encrypts the connection so that sensitive information such as passwords, personal data, or payment details cannot be read or modified by attackers.
TLS works by establishing a secure session through a process known as the TLS handshake. During this handshake, the client and server agree on encryption algorithms, verify the server’s identity using a digital certificate issued by a trusted Certificate Authority, and generate shared secret keys. Once the handshake is complete, all data exchanged in the session is encrypted and protected against tampering.
TLS evolved from SSL (Secure Sockets Layer), which is now fully deprecated due to security weaknesses. Although people still commonly refer to “SSL certificates,” modern secure connections use TLS, not SSL. Over time, TLS has been refined to remove insecure features and strengthen cryptography, with TLS 1.2 and TLS 1.3 being the widely accepted versions today.
Beyond web browsing, TLS is used across many internet services, including email transmission, APIs, messaging applications, and VPNs. It is a foundational technology of the modern internet, providing trust, confidentiality, and integrity for digital communication.