The history of Sudoku
Sudoku has a Japanese name, but it was first published in the United States, and it became famous because of a British newspaper.
The short version: an American puzzle magazine printed it in 1979 under the name Number Place. A Japanese publisher picked it up in 1984 and gave it the name Sudoku. Twenty years later, a retired judge from New Zealand persuaded The Times in London to run it, and within a year it was everywhere.
Timeline
| 1782 | Leonhard Euler writes about Latin squares, grids where each symbol appears once in every row and column. |
|---|---|
| 1890s | French newspapers print number puzzles built on 9 by 9 magic squares, some very close to Sudoku. |
| 1979 | Dell Pencil Puzzles and Word Games prints Number Place, the puzzle we now call Sudoku. It is credited to Howard Garns. |
| 1984 | Nikoli brings the puzzle to Japan and gives it the name that becomes Sudoku. |
| 2004 | The Times in London starts printing Sudoku in November, supplied by Wayne Gould. |
| 2005 | Sudoku spreads to newspapers around the world and becomes a craze. |
| 2006 | The first World Sudoku Championship is held in Lucca, Italy. |
| 2012 | Researchers show by computer search that a Sudoku needs at least 17 clues to have one solution. |
Before Sudoku: Latin squares
The idea of a grid where every symbol appears once in each row and column is old. The Swiss mathematician Leonhard Euler studied these grids in the 1780s and called them Latin squares, because he used Latin letters as the symbols. A finished Sudoku is a Latin square with one extra rule: the nine boxes must also each contain every number.
Euler was interested in the mathematics, not in puzzles for readers. Nobody was being asked to fill in blanks.
French newspapers in the 1890s
The closest early relatives appeared in French newspapers at the end of the nineteenth century. Papers such as Le Siècle and La France printed number puzzles based on magic squares, where rows, columns and diagonals had to add up to the same total. Some of these used a 9 by 9 grid, and in a few the 3 by 3 blocks also held the numbers 1 to 9 once each, even though the blocks were not marked. They faded out in the early twentieth century and did not lead directly to the modern game.
Number Place, 1979
The puzzle as we know it first appeared in 1979 in Dell Pencil Puzzles and Word Games, an American magazine. It was called Number Place. Dell did not print the names of its puzzle makers, but the puzzle has since been credited to Howard Garns, a retired architect from Indiana. Number Place already had everything the modern game has: a 9 by 9 grid, nine marked boxes and some numbers given at the start.
A new name in Japan, 1984
In 1984 the Japanese puzzle company Nikoli published the puzzle in its magazine under a long name that roughly means "the numbers must be single". It was soon cut down to Sudoku, from the Japanese for number and single. Nikoli's president, Maki Kaji, is often called the godfather of Sudoku for this.
Nikoli also shaped how good puzzles look. Its editors preferred puzzles where the given numbers form a symmetric pattern, and they cared about puzzles that can be solved by logic rather than guessing. The puzzles on this site keep both traditions: the givens are placed in mirrored pairs, and each puzzle has exactly one answer.
The British boom, 2004
Wayne Gould, a New Zealander who had worked as a judge in Hong Kong, came across Sudoku in a Tokyo bookshop in 1997. He spent years writing a computer program that could produce puzzles quickly, then offered them to newspapers. The Times in London began printing them in November 2004. Other British papers followed within weeks, and by 2005 Sudoku was running in newspapers across Europe, North America and Australia.
Part of the appeal was that it needs no language. A puzzle printed in London works just as well in Tokyo or Buenos Aires, and anyone can learn the rule in a few seconds.
Competitions
The first World Sudoku Championship took place in Lucca, Italy, in 2006. It was won by Jana Tylová of the Czech Republic. The championship has been held most years since, alongside a wider World Puzzle Championship, and top solvers finish hard puzzles in a few minutes.
What mathematicians found
Sudoku also turned out to be interesting to mathematicians. In 2005 Bertram Felgenhauer and Frazer Jarvis counted how many completed 9 by 9 grids exist. The answer is 6,670,903,752,021,072,936,960. Many of those are the same grid with the numbers relabelled or the rows shuffled, and once those are grouped together there are about 5.5 billion truly different grids.
Another long open question was how few clues a puzzle can have and still have only one answer. In 2012 Gary McGuire, Bastian Tugemann and Gilles Civario used a large computer search to show that 16 clues are never enough. The minimum is 17. We wrote more about that in the fewest clues a Sudoku can have.
Sudoku today
The puzzle has grown a large family of variants. Killer Sudoku adds cages whose numbers must add up to a total. Mini Sudoku shrinks the grid to 6 by 6. Giant versions use 16 by 16 grids with letters or two-digit numbers. The classic 9 by 9 version is still the one most people play every day, in print, in apps and in the browser.