How does https work

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Last updated: April 8, 2026

Quick Answer: HTTPS (Hypertext Transfer Protocol Secure) is the secure version of HTTP that encrypts data between web browsers and servers using TLS/SSL protocols. It was first implemented by Netscape in 1994 with SSL 2.0, and today over 90% of web pages loaded in Chrome use HTTPS. This encryption prevents eavesdropping, tampering, and man-in-the-middle attacks by establishing authenticated and encrypted connections.

Key Facts

HTTPS usage grew from 39.5% of websites in 2015 to over 90% in 2023 according to W3Techs
Google began prioritizing HTTPS sites in search rankings starting in 2014
The first HTTPS specification was published in RFC 2818 in May 2000
Let's Encrypt has issued over 3 billion TLS certificates since launching in 2015
HTTPS uses port 443 by default compared to HTTP's port 80

Overview

HTTPS (Hypertext Transfer Protocol Secure) is the foundation of secure communication on the World Wide Web, providing authentication, encryption, and integrity for data transmitted between clients and servers. Developed as an extension of HTTP, HTTPS emerged in response to growing security concerns as e-commerce and online transactions became more prevalent in the 1990s. Netscape Communications Corporation first implemented HTTPS in 1994 with the introduction of SSL (Secure Sockets Layer) 2.0 for their Netscape Navigator browser. The protocol evolved through SSL 3.0 (1996) to TLS (Transport Layer Security) 1.0 (1999), with subsequent versions improving security and performance. Major milestones include Google's 2014 announcement to prioritize HTTPS sites in search rankings and the 2015 launch of Let's Encrypt, which dramatically increased HTTPS adoption by providing free TLS certificates. Today, HTTPS has become the standard for web security, with browsers like Chrome and Firefox marking HTTP sites as "not secure" since 2017.

How It Works

HTTPS operates through a multi-step process that establishes a secure connection before any data transmission occurs. The process begins with the TLS handshake, where the client (browser) and server exchange cryptographic information to authenticate identities and establish encryption parameters. During this handshake, the server presents its TLS certificate containing a public key, which the client verifies against trusted Certificate Authorities (CAs). Once authenticated, the client and server generate session keys using asymmetric encryption, then switch to faster symmetric encryption for the actual data transfer. This symmetric encryption typically uses algorithms like AES (Advanced Encryption Standard) with 128-bit or 256-bit keys, providing strong protection against interception. HTTPS also includes message authentication codes (MACs) to ensure data integrity, preventing tampering during transmission. The entire process happens transparently to users, who simply see the padlock icon in their browser's address bar indicating a secure connection.

Why It Matters

HTTPS is crucial for protecting sensitive information in today's digital world, particularly for e-commerce, online banking, healthcare portals, and government services where personal data like credit card numbers, passwords, and medical records are transmitted. Beyond encryption, HTTPS provides authentication that helps prevent phishing attacks by verifying website identities, and integrity protection that ensures data isn't modified in transit. The protocol has become essential for regulatory compliance with standards like PCI DSS for payment processing and GDPR for data protection. HTTPS also enables modern web features like geolocation APIs and progressive web apps that require secure contexts. As cyber threats continue to evolve, HTTPS serves as a fundamental security layer that builds user trust and enables the secure expansion of internet services worldwide.