History of the Internet: From ARPANET to the World Wide Web

The First Packet Crashed the Network

On October 29, 1969, at 10:30 PM, UCLA student programmer Charley Kline sat at an SDS Sigma 7 mainframe and attempted to transmit the word "login" to a machine at the Stanford Research Institute (SRI) 360 miles away. The receiving system at SRI crashed after registering only two characters — "l" and "o." The connection was restored within an hour, and the full "login" command completed at 10:30 PM. Forty minutes of failed transmission marked the birth of ARPANET, the packet-switched network funded by the U.S. Department of Defense Advanced Research Projects Agency that would evolve, over the next five decades, into the global internet.

ARPANET: The Architecture That Changed Everything

ARPANET was not the first computer network, but it introduced the architectural principles that made global networking possible. Its key innovation was packet switching — a concept developed independently by Paul Baran at RAND Corporation (1964) and Donald Davies at Britain's National Physical Laboratory (1965). Rather than establishing a dedicated circuit between two endpoints as telephone networks did, packet switching breaks messages into discrete packets that travel independently across the network, potentially via different routes, and reassemble at the destination.

• 1969: ARPANET connects four nodes — UCLA, SRI, UC Santa Barbara, and the University of Utah — using Interface Message Processors (IMPs) built by Bolt Beranek and Newman.
• 1971: Ray Tomlinson sends the first email between two ARPANET-connected machines, choosing the @ symbol to separate username from host name. The first message content was unremarkable test strings.
• 1972: ARPANET is demonstrated publicly at the International Conference on Computer Communication in Washington D.C., connecting 40 machines and impressing an international audience.
• 1973: Connections to University College London and Norway's Royal Radar Establishment make ARPANET international for the first time.

TCP/IP: The Protocol That Unified the Network

By the late 1970s, ARPANET existed alongside incompatible networks — including CSNET, SATNET, and packet radio networks — each using different communication protocols. The critical problem was internetworking: routing data between networks that spoke different technical languages.

Vinton Cerf and Robert Kahn published "A Protocol for Packet Network Intercommunication" in IEEE Transactions on Communications in May 1974, proposing the Transmission Control Protocol (TCP). The design was later split into TCP and the Internet Protocol (IP), allowing flexible layering. On January 1, 1983 — designated "Flag Day" — ARPANET officially switched from the Network Control Protocol (NCP) to TCP/IP. All connected machines had to complete the transition simultaneously; there was no backward-compatible migration path. That date marks the technical birth of the modern internet.

Tim Berners-Lee and the World Wide Web

The internet existed for two decades before most people had heard of it. What changed in 1991 was not the network itself but the application layer that made it usable. Tim Berners-Lee, a British physicist at CERN in Geneva, proposed an information management system in a 1989 memo titled "Information Management: A Proposal." His supervisor famously annotated the document "Vague but exciting."

Berners-Lee implemented three technologies that together constituted the World Wide Web: HTML (HyperText Markup Language) for creating documents, HTTP (HyperText Transfer Protocol) for transmitting them, and URLs (Uniform Resource Locators) for addressing them. On August 6, 1991, he published the first website — http://info.cern.ch — explaining the web project itself. CERN made the underlying web technology freely available on April 30, 1993, renouncing all intellectual property claims. That decision accelerated adoption more than any marketing effort could have.

MOSAIC and Commercialization

The web's technical elegance did not immediately produce mass adoption. The early web required Unix command-line expertise to navigate. The National Center for Supercomputing Applications (NCSA) at the University of Illinois released MOSAIC in February 1993 — the first web browser to display images inline with text on a graphical interface. Within a year, MOSAIC had been downloaded over two million times.

• Marc Andreessen, one of MOSAIC's authors, co-founded Mosaic Communications Corporation in 1994, later renamed Netscape, which launched the first commercial web browser: Netscape Navigator.
• The U.S. Congress passed the Scientific and Advanced-Technology Act in 1992 and the NSFNet commercialization policy took effect in 1995, lifting restrictions on commercial use of the internet backbone.
• America Online (AOL) distributed over one billion floppy disks and CDs containing its internet software between 1993 and 2006, onboarding tens of millions of first-time internet users.
• By 1995, the web hosted fewer than 25,000 sites. By 2000, the count exceeded 17 million. By 2024, an estimated 1.09 billion websites exist, though approximately 82% are inactive.

From Government Tool to Global Infrastructure

ARPANET was formally decommissioned on February 28, 1991, having long been superseded by the commercial internet it helped create. The network that began with four nodes and a crash now carries an estimated 400 exabytes of data per month. The architectural choices made in 1969 — decentralized routing, packet switching, open protocols — were not designed to build a global communications system. They were designed to route around network failures in a military communications context. Their suitability for everything that followed was a consequence of simplicity and openness, not foresight.