Classic Sudoku
Fill a 9x9 grid so every row, column and 3x3 box holds the digits 1 to 9 once. The classic puzzle and the best place to start.
Sudoku Wiki
This sudoku wiki explains the sudoku rules of every Sudoku69 game, the techniques that solve them and the guides that tie it together. It helps beginners learn a first puzzle and experienced players reach the harder levels, in all six difficulty levels of every mode.
Three ways to play
Killer Sudoku
A 9x9 grid split into cages with target sums. No digit repeats inside a cage, and harder levels give no starting digits at all.
Giant Sudoku 16x16
A bigger grid with 16 symbols (1 to 9 and A to G) and 4x4 boxes. Same logic as classic, but each solve takes much longer.
Solving techniques
Sudoku strategies form a ladder, from simple singles up to forcing nets. There are 38 techniques in total, and learning them in order works best. Each article has a worked example and matches a difficulty level, so the full solving techniques list shows what to learn next.
Best reading for puzzle players
Start here
- How to Play Sudoku: Rules and Your First MoveHow to play sudoku in minutes: the rules for sudoku, how the 9x9 grid works, a worked first move, pencil marks and where a beginner should start.
- Sudoku Keyboard ShortcutsSudoku keyboard shortcuts: play without the mouse. Digits, arrows, notes, undo, redo, erase, pause, 16x16 letters and Tab keys around the site.
- How to Solve a Sudoku Puzzle, Step by StepHow to do sudoku with a method that always shows your next move: scan for singles, add pencil marks, use pairs. Includes a real puzzle solved move by move.
- Sudoku Tips for Beginners: Solve Without GuessingTips for solving sudoku that work: scan in a fixed order, use crosshatching and pencil marks, check every move and never guess. Includes a worked Easy example.
- Sudoku Difficulty Levels: Easy to LegendarySudoku levels explained: how sudoku difficulty is rated, what Easy to Legendary each need, why clue count misleads and how to pick the level that suits you.
Killer Sudoku
- How to Play Killer Sudoku: Cages, Sums, 45 RuleKiller sudoku rules in plain words: cages, sums, no repeats and the 45 rule. Learn how to play killer sudoku, how it differs from classic, and your first moves.
- Killer Sudoku Combinations Chart and Cheat SheetKiller sudoku combinations for every cage size and sum in one chart. A killer sudoku cheat sheet with single-combination cages marked, ready to use mid-solve.
- Innies and Outies in Killer Sudoku45 rule sudoku explained: innies and outies read a digit straight off a Killer cage layout, before you write a single candidate.
- Killer Sudoku Cage CombinationsKiller cage sudoku sums with only one possible digit set are forced. Learn the unique sums and lock digits in on your first pass.
- Math Sudoku: Killer, Arrow, Sandwich and KakuroSum sudoku (Killer) and its relatives compared: Little Killer, Sandwich, Arrow and Kakuro. How Killer rates against classic and the cage techniques you need.
First techniques to learn
- Naked and Hidden SinglesSudoku hidden singles and naked singles are the two ways a puzzle forces a digit into a cell. Learn to spot both and finish easy grids without guessing.
- Naked and Hidden PairsHidden pairs sudoku technique, plus naked pairs: how two cells lock two digits and clear the candidates that block your next single.
- Pointing PairsPointing pairs sudoku technique: a locked candidate that traps a digit in one line of a box and clears it from the rest of that line.
- X-Wing Sudoku TechniqueX-Wing sudoku technique: when one digit sits in only two columns across two rows, you can delete it from the rest of those columns.
- Y-Wing (XY-Wing) Sudoku TechniqueSudoku XY-Wing, also called the Y-Wing: a pivot cell and two pincers sharing three digits force an elimination in every cell that sees both pincers.
Beyond the grid
- Sudoku Variants: Types You Can Play and LearnTypes of sudoku and sudoku variations compared by family: extra regions, cages, lines, bigger grids. See the skills each needs and which you can play here.
- History of Sudoku: Who Invented It and WhenSudoku meaning and history: who invented the puzzle, Howard Garns and Dell Number Place in 1979, Nikoli in 1984 and The Times in 2004, with a timeline.
- Sudoku Mathematics: Grids, Clues, SolutionsSudoku mathematics in plain words: how many grids exist, why 17 clues is the minimum, and whether every puzzle has one solution. Is sudoku math? With sources.
- The Hardest Sudoku Ever: What Makes a Grid BrutalThe hardest sudoku ever: what the world's hardest sudoku headlines mean, how difficulty is rated, and our own hardest grids (killer 12.8, classic 11.1).
- Is Sudoku Good for Your Brain? What Studies SayIs sudoku good for your brain? The benefits of sudoku in studies on memory, focus and dementia risk, where evidence is weak, and how to get the most from it.