Learn
Sudoku is built on a small set of logical techniques. Master them in order and you can solve any puzzle without guessing.
Start here
The two techniques you'll use on every single puzzle. If you're new to sudoku, this is all you need.
Pairs and triples
When singles aren't enough, start looking for cells that share candidates.
Intermediate patterns
These techniques let you eliminate candidates by studying how they're distributed across rows, columns, and boxes.
- Hidden PairTwo values that appear as candidates in only two cells of a unit.
- Hidden TripleThree values confined to exactly three cells in a unit.
- Pointing PairsA candidate in a box restricted to a single row or column.
- Box/Line ReductionA candidate in a row or column restricted to a single box.
- Naked QuadFour cells in a unit whose combined candidates contain exactly four values.
- Hidden QuadFour values confined to exactly four cells in a unit.
Advanced strategies
For tougher puzzles. These require spotting patterns that span multiple rows and columns at once.
- X-WingA candidate confined to two columns in exactly two rows, forming a rectangle.
- SwordfishA candidate confined to three columns across exactly three rows.
- XY-WingA pivot cell with two wings that share eliminating candidates.
- Simple ColoringAlternating chains of conjugate pairs reveal contradictions.
The deep end
Rarely needed, but satisfying when you spot them. These are for the most challenging puzzles.