The History of Online Sudoku: From Newspaper to App

Sudoku didn’t reach mass audiences until 2004. Online Sudoku followed within months. The history of online sudoku is shorter than most people guess — the puzzle itself only acquired its modern name in 1984, and it only became a global obsession after a retired New Zealand judge named Wayne Gould pitched The Times of London on running a daily one. From there, the web caught up fast.

What Sudoku actually is

Sudoku is a number-placement puzzle: a 9×9 grid divided into nine 3×3 boxes. The solver fills in digits 1 through 9 such that each row, column, and box contains each digit exactly once. A handful of digits are filled in at the start to constrain the solution. There’s only one valid solution per well-formed puzzle. The arithmetic is irrelevant — the digits could be any nine distinct symbols. Sudoku is a logic puzzle dressed as a math puzzle.

The format dates back to the late 1970s. American architect Howard Garns is generally credited as the designer of the modern version, which appeared in Dell Magazines from 1979 under the title “Number Place.” The puzzle was popular in Japan from the mid-1980s, where Nikoli, a Japanese puzzle publisher, renamed it “Sudoku” (a contraction of “Sūji wa dokushin ni kagiru” — “the digits are limited to one”). For two decades it was a Japanese specialty product.

Wayne Gould and the 2004 Times launch

Wayne Gould, a retired judge from Hong Kong, encountered Sudoku in a Tokyo bookstore in 1997. He wrote a computer program to generate puzzles, then spent years pitching newspapers on running them. The Times of London bit in November 2004 and launched a daily Sudoku. The puzzle took off immediately. Within months it was running in the Daily Telegraph, the Daily Mail, the New York Post, USA Today, and a long list of others.

Gould’s contribution wasn’t designing the puzzle — he didn’t — but doing what nobody had done before: industrializing the supply. His software could generate puzzles of graded difficulty at scale, which meant newspapers could publish a fresh daily puzzle without commissioning a constructor. Sudoku was the first major puzzle genre to scale via algorithm rather than authorship, which was directly why it could fill newspaper grids worldwide in a year.

2005 and the global boom

By the summer of 2005, Sudoku was everywhere. Book stalls filled with Sudoku collections. Schools introduced Sudoku as a logic exercise. Word-of-mouth carried it across demographics — older solvers loved that the puzzle required no language, younger ones loved the streak of fast solves. The numbers don’t lie: 2005 was the year the puzzle world picked up a new pillar genre alongside crossword and word search.

The web caught up quickly. By mid-2005, dozens of free Sudoku sites had launched, most using Gould-style generators (or their own equivalents). The puzzle was simple enough to encode in JavaScript and basic HTML — a 9×9 grid, click-to-enter digits, an auto-solver and check function — that any competent web developer could build a respectable site in a weekend.

Web Sudoku and the free-puzzle web

Web Sudoku, launched in 2005 by Gideon Greenspan and Rachel Lee, became one of the most-used free online Sudoku sites and is still operating. It offers four difficulty levels (Easy, Medium, Hard, Evil), generates fresh puzzles on demand, and runs in any browser. The interface is unfussy: click a cell, type a number, the page checks for conflicts. No login required.

Web Sudoku helped define the conventions of the online format. Pencil marks (small candidate digits in the corner of a cell), conflict highlighting, undo, and a check button became standard. Newer sites added more features — automatic notes, hint systems, color marking, theme support — but the core interaction stayed the same.

Other free options proliferated. Sudoku.com (operated by Easybrain) became one of the highest-traffic puzzle sites in the world by 2020, ranking in the millions of daily players. New York Times added Sudoku to its games lineup. The Guardian, Washington Post, and most major newspapers run free or low-paywall Sudoku. There’s no shortage of grids.

The app era

iOS launched in 2007, the App Store in 2008, and Sudoku was on Day One. The puzzle’s mechanics — short sessions, no opponent, infinite supply — matched mobile perfectly. By the early 2010s, Sudoku apps were among the highest-grossing puzzle category on both iOS and Android, dominated by Easybrain’s Sudoku.com and a long tail of competing apps.

The mobile shift changed how people solved. Pencil marks became a tap. Mistakes were caught immediately. The auto-fill notes feature — where the app populates every cell’s possible candidates — turned what used to be a careful pen-and-paper exercise into something faster and more puzzle-focused. Purists complain that mobile features make Sudoku too easy. The numbers say players don’t mind.

Variants and the puzzle’s deepening

The standard 9×9 Sudoku is now joined by a long list of variants. Killer Sudoku adds cage sums. Hyper Sudoku adds extra constraint regions. Greater Than Sudoku replaces some clues with inequality signs. Samurai Sudoku links five 9×9 grids in an overlapping shape. The “puzzle hunt” community on YouTube — most prominently Cracking The Cryptic, hosted by Simon Anthony and Mark Goodliffe since 2017 — has done more than anyone to bring these variants to mainstream solvers.

Cracking The Cryptic’s videos showcase constructed puzzles that push the format hard. The famous “Miracle Sudoku” video from 2020 drew millions of views — a puzzle by Mitchell Lee with only two starting digits but a uniquely constrained ruleset. That moment broadened the audience for advanced Sudoku considerably and reminded the puzzle world that there was still meaningful design space inside a 9×9 grid.

Sudoku versus the broader puzzle web

Compared to crosswords, online Sudoku has always skewed more language-agnostic and globally distributed. Crosswords are tied to a specific language; Sudoku works in any one. That explains some of the format’s reach into markets where English-language crossword traffic is weak. It also explains why Sudoku app teams are often based outside the major English-language media companies — Easybrain, the dominant publisher, is headquartered in Cyprus.

The genre’s stability is striking. The puzzle has barely changed in 20 years. The constraints, the grid size, the solving heuristics — all of it has held. For broader context on similar pen-and-paper puzzles that moved online, see our piece on games like Sudoku, and if you’re new to the format, our how to solve Sudoku guide covers the basic techniques.

Frequently asked questions

When did Sudoku become popular online?

Online Sudoku boomed in 2005, the year after Wayne Gould’s daily Sudoku launched in The Times of London. Free Sudoku sites appeared in waves through 2005 and 2006, and Web Sudoku launched in 2005 became one of the longest-running examples.

Who invented Sudoku?

Sudoku’s modern form is generally credited to American architect Howard Garns, who designed the puzzle for Dell Magazines in 1979 under the title “Number Place.” It was renamed Sudoku by Japanese puzzle publisher Nikoli in 1986.

Is Sudoku.com the same as Web Sudoku?

No. Sudoku.com is operated by Easybrain and is a separate site and app, launched later. Web Sudoku has been independently operated since 2005 by Gideon Greenspan and Rachel Lee. Both are free to play.

What’s a Killer Sudoku?

Killer Sudoku is a variant where some cells are grouped into “cages” with a sum constraint — the digits in each cage must add to a specified total without repeating within the cage. Standard Sudoku rules still apply on top of the cage constraints.

Can a computer always solve Sudoku?

A well-formed Sudoku has exactly one solution, and any of several algorithms (constraint propagation, backtracking, dancing links) will find it quickly on modern hardware. The interesting question for human solvers is which logical techniques are required — that’s what determines a puzzle’s difficulty rating.

The takeaway

Sudoku reached the world via a 2004 newspaper launch and was online within a year. The format has barely evolved because it didn’t need to — the original 9×9 grid is one of the great puzzle designs of the last century. From Web Sudoku in 2005 to Sudoku.com today, the online history is essentially a story of distribution: getting the puzzle in front of more people on more devices. If you want a different brand of quick browser distraction, the Chrome Dino game needs no setup. For more historical detail, see the Sudoku Wikipedia article.