Learn Sudoku
Solve any Sudoku without guessing
Twelve logical moves solve almost every Sudoku. These guides teach them in the order you'll need them, each with real positions from Ninebloom's puzzles, found and checked by the app's own hint engine.
The technique ladder
Each step builds on the one before. Easy puzzles need only the first two; the hardest need moves from the bottom of the list.
Beginner
Naked single
A cell with only one digit left.
Easy
Hidden single
A digit with only one place left in a row, column or box.
Medium
Naked pair
Two cells share the same two candidates.
Medium
Pointing pair
A digit in a box lines up in one row or column.
Expert
X-Wing
A rectangle of one digit across two lines.
Fiendish
Swordfish
An X-Wing across three lines.
New to Sudoku, or getting better?
How to play Sudoku
The rules in one minute, and the first moves to make on an empty grid.
What makes a Sudoku hard
Why difficulty is about the techniques a puzzle needs, not the number of clues.
Stuck on a Sudoku?
A checklist that finds your next logical move.
Killer Sudoku
The rules, the opening moves and the full cage combinations chart.
Ways to play
Mini, Diagonal, Jigsaw, Thermo, Anti-knight, Giant 16×16 and Windoku, explained.
Accessible Sudoku
Playing with a screen reader, large print or high contrast.
Why the examples are different here
Most technique guides use one hand-made diagram. Every board on this site is a real position from a puzzle in Ninebloom, found by the same hint engine the app uses, with the exact cells and eliminations it proves. Under each board is a code: paste it into Ninebloom's Your own puzzle screen and you're playing that position, with hints that explain every step from there.
