Tic tac toe in its earliest known form was invented around 100 BC in ancient Rome. The modern version with Xs and Os as we know it today took shape in England in the early 19th century, and the name "tic tac toe" became common in America by the early 20th century.

Here's the full timeline.

~100 BC: Ancient Rome

The story starts with a Roman game called Terni Lapilli, Latin for "three pebbles." Archaeologists have found the distinctive 3×3 grid scratched into stone surfaces all over the Roman Empire. On pavements. On walls. On the steps of the Colosseum itself.

The Roman version was slightly different from what we play today. Each player had only three pieces and had to slide them around the board rather than placing new ones. But the objective was identical: get three in a row.

Nobody knows exactly who invented it or when, but the earliest physical evidence dates to around 100 BC, making the game well over 2,000 years old.

The grid has also been found in Roman military camps in Britain, on pavements in Pompeii, and at sites across the broader empire. The spread suggests it was genuinely popular rather than a local curiosity. Some historians believe Roman soldiers carried the game from city to city as they moved through the empire.

You can play Terni Lapilli free in your browser if you want to try the original Roman version.

Early 19th century: England

The version we play today (placing a new X or O on each turn until someone wins or the board fills up) appears to have developed in England in the early 1800s.

The British called it noughts and crosses, which describes exactly what you do: place noughts (the O) and crosses (the X) on a grid. The first known printed reference to "noughts and crosses" appears around 1864, but the game was already well established as a children's pastime by then.

The shift from sliding pieces to placing a new one each turn made the game faster and more accessible. A complete game could take less than a minute, and all you needed was a stick to draw a grid in the dirt. It became one of the first strategy games most people ever learned to play.

Late 19th century: America

The name "tic tac toe" arrived in America in the late 19th century, though it originally referred to a completely different game: a children's toy where you threw a pencil at a slate and scored points based on where it landed.

Somewhere around the turn of the 20th century the name migrated to the grid game. By the early 1900s "tic tac toe" had firmly stuck in American English while Britain kept "noughts and crosses." Same game, different names, much like football and soccer.

1952: The first computer game

Here is the part most people don't know. In 1952 a Cambridge University PhD student named Alexander Douglas built a computer version of the game called OXO as part of his thesis on human-computer interaction.

OXO ran on the EDSAC computer and displayed the game on a cathode ray tube screen. It played a perfect game and could never lose. And it predates Pong by twenty years, making it one of the strongest candidates for the title of the first video game ever made.

EDSAC stands for Electronic Delay Storage Automatic Calculator, one of the first stored-programme computers ever built. Douglas chose tic tac toe deliberately: it was simple enough for early hardware to handle, but complex enough to demonstrate that a machine could make decisions. Players entered their moves using a rotary telephone dial, with each number corresponding to a square on the grid.

Today

Tic tac toe is now one of the most widely played games in the world, available on every device imaginable. Mathematicians classify it as a solved game: with perfect play from both sides it always ends in a draw. That's why it stops being interesting to adults pretty quickly, but remains a perfect first strategy game for children.

The total number of possible tic tac toe games is 255,168, but when you account for rotations and reflections it drops to around 26,830. Every single one of them is determined entirely by the players' decisions. There is no luck involved at all.

Why does the game always end in a draw?

The first player can always avoid losing if they play correctly. The centre square is the strongest opening: it belongs to four possible winning lines (two diagonals, one row, one column), making it the most contested position on the board.

If the first player takes the centre and responds correctly to every threat after that, the game cannot be lost. This is what mathematicians mean by a solved game: the outcome under perfect play is fixed, and with both sides playing well the result is always a draw.

Children often work this out on their own. After enough games, most kids around age eight or nine figure out that the centre and corners are the squares that matter. Once both players know that, every game ends the same way, and the game stops being a game in the usual sense. That is exactly what makes it a good teaching tool for basic game theory and strategic thinking.

From a Roman soldier scratching a grid into a pavement to a Cambridge computer playing a flawless game on a cathode ray tube, the history of tic tac toe is surprisingly rich for something you can draw in ten seconds.

Play tic tac toe free →

Sources