Learn Sudoku: Rules and Solving Techniques
Every lesson here is played on the same grid you solve puzzles on. You read a few lines, place a digit, and the grid tells you whether it was forced. Start with the rules if you have never played. If you can already fill an easy puzzle, go straight to the techniques: each one builds on the ones before it.
- 8 lessons
- 25 min
- Free, no sign-up
Unit 1
The rules
Rows, columns and boxes, how to enter a digit, and what a clash is. A few minutes, and you can start your first puzzle.
Unit 2
Solving techniques
Seven ways to prove where a digit goes, roughly from easiest to hardest: the naked single and the hidden single, then the naked pair, pointing pair, box/line reduction, hidden pair and X-wing. Singles alone finish every easy, medium and hard daily puzzle here; the expert ones are where the rest come in. Every position is a real puzzle in which the lesson's technique, and nothing taught before it, finds the next digit.
Naked Single: The First Sudoku Technique
A naked single is a sudoku cell with one candidate left. Learn to list a cell's candidates and spot naked singles on a live grid.Hidden Single in Sudoku: The Only Place Left
Naked Pair in Sudoku: Two Cells, Two Digits
A naked pair is two cells in a row, column or box with the same two candidates. Learn how it clears both digits from the rest of that row, column or box.Pointing Pair in Sudoku: Clear a Row or Column
When a digit's candidates in a box all lie in one row or column, they point along it. Learn the pointing pair on a live sudoku grid.Box/Line Reduction in Sudoku (Claiming)
When a row or column's candidates for a digit all fall in one box, the line claims it. Learn box/line reduction, or claiming, on a live grid.Hidden Pair in Sudoku: Two Digits, Two Cells
X-Wing in Sudoku: Explained on a Live Grid
An X-wing is one digit in two rows, each with two places in the same two columns. Learn the X-wing and use it to crack a hard sudoku.