Why it is disputed
Asking which game was the first is harder than it sounds. Some people mean the first game that ran on a digital computer. Others mean the first with a graphical display, or the first intended for entertainment, or the first anyone could play on a regular basis. Different definitions give different answers, and the early history is full of experiments made by researchers who did not think of them as products. Several important examples are described below, in rough date order.
Games on early computers
In 1951, at the Festival of Britain, visitors could play Nim against a machine called Nimrod, built by Ferranti. It was a special-purpose computer designed to play the simple game of Nim, and it was meant to demonstrate the technology. It had a panel of lights rather than a screen with moving images.
In 1952, A. S. Douglas wrote a program, now called OXO, as part of his doctoral work at the University of Cambridge. It let a human play noughts and crosses, which Americans call tic-tac-toe, against the computer on the EDSAC. The EDSAC used cathode ray tubes to display the contents of its memory, and OXO drew its board on one of them. Also in the early 1950s, Christopher Strachey wrote a program for the Manchester Ferranti Mark 1 that played draughts, or checkers, and Dietrich Prinz wrote a chess-related routine, though early chess programs could not play a full game.
These were programs on research machines. Some historians prefer to count them as the earliest computer games, while others point out that they were demonstrations or experiments rather than a product for play.
Tennis for Two
In 1958, William Higinbotham, a physicist at Brookhaven National Laboratory in New York, created Tennis for Two for a visitors’ open day. It used a small analog computer and an oscilloscope screen, showing a side view of a tennis court with a ball whose path was affected by simulated gravity. Players used a controller with a knob and a button. It was popular with visitors, and Higinbotham did not patent it or pursue it commercially.
Because it ran on analog hardware, some definitions do not treat it as a computer game in the strict digital sense. It is frequently cited as one of the first games with a real-time display and dedicated controllers, and the lines of this dispute are about definitions, not facts.
Spacewar!
The best-known early game on a digital computer is Spacewar!, developed in 1962 at the Massachusetts Institute of Technology. Steve Russell led the work with others, including Martin Graetz and Wayne Wiitanen, on a DEC PDP-1, a minicomputer with a graphical display. Two spaceships controlled by players fire at each other while a star at the center pulls on them with gravity.
The game spread to other universities and research labs because the program could be copied and DEC reportedly used it as a test for new machines. The source code was shared, and programmers added features. Its influence was large: it inspired later arcade games and showed what interactive entertainment might look like. The arcade version of the idea became Computer Space in 1971, a topic with its own story.
Other games of the 1960s
Other programs and games kept appearing. Many were text-based and ran on time-shared mainframes. Students at Dartmouth College developed the BASIC language in 1964, and later BASIC game collections spread through schools and magazines. Hobbyists and researchers wrote simple simulations, quizzes and strategy games. Few were saved, and records from this period are patchy, which makes any claim to be the first risky.
Meanwhile, Ralph Baer, an engineer working for a defense electronics company, began in the 1960s to develop ways to play games on a television set, which led to the Magnavox Odyssey home console, released in 1972. That story belongs to the history of consoles, not computers as such.
Why none of them became a market
Early computers cost huge sums, and time on them was rationed. A game would not be a good use of a machine worth hundreds of thousands of dollars, so most games were written in spare moments by enthusiasts. Games were not sold, and the idea of a mass market had to wait for cheap chips and arcade hardware.
How to answer the question
If the definition is “a digital computer game,” the answers are Nimrod, OXO or the Strachey draughts program, depending on whether special-purpose machines and display requirements are counted. If the definition is “a real-time video game with a display,” Tennis for Two and Spacewar! are the usual choices. If the definition is “a game people played widely,” Spacewar! is a good candidate within the research community. A careful writer will say “among the first” instead of “the first.”
Why these experiments mattered
These early games were not products, but they proved that people enjoy interacting with a computer for fun. They gave programmers practice in real-time response, graphics and simple physics, skills that later mattered for the video game industry, from the Snake game on early mobile phones to VR gaming. The step from laboratory curiosity to coin-operated machine took years and relied on cheaper hardware.