Learn them in this order
The techniques below are ranked by what they cost you in effort, which is also the order the site's own solver tries them in. Naked singles finish almost any easy puzzle. Add hidden singles for medium and hard, and locked candidates for the harder hard grids and most expert ones. Pairs, wings and fish are what the toughest expert grids come down to.
| Technique | Where you meet it | What it does |
|---|---|---|
| Naked singles | Easy | One cell, one possible digit |
| Hidden singles | Medium and up | One digit, one possible cell in a unit |
| Pointing pairs | Hard and expert | A digit trapped on one line inside a box |
| Naked pairs | Some expert grids | Two cells that own two digits between them |
| Hidden pairs | Some expert grids | Two digits that fit in only two cells |
| X-Wing | A few expert grids | A digit boxed into a rectangle |
| XY-Wing | A few expert grids | Three linked cells that force one digit out |
| Swordfish | Rarely, at expert | An X-Wing across three lines instead of two |
How to actually learn one
Reading about a technique rarely makes it stick. Play a puzzle at the difficulty where it appears, and when you get stuck press the hint button — it names the technique it used and explains the elimination on the position in front of you. Two or three of those and you will start seeing the pattern before the button does.
Every example on these pages was mined from a real generated puzzle by the same solver that grades the site's difficulty levels. If a diagram says a technique applies, it applies.
Common questions
Which Sudoku technique should I learn first?
Hidden singles. They are the most common move in every puzzle from easy to expert, and they need no pencil marks.
How many techniques do I actually need?
Two will finish easy puzzles, four will finish hard ones. The advanced patterns only matter at expert level.
Do I need to learn chains and colouring?
Not for this site. Every published puzzle can be solved with the eight techniques listed here, which is checked during generation.