When advanced techniques begin
Advanced Sudoku techniques take over where singles stop: instead of placing digits, they remove candidates using logic that spans several cells or the whole grid. You will need them mostly in hard and evil puzzles.
Before starting this cluster, be comfortable with pencil marks and the basic singles. Every technique here reads candidate lists, so their accuracy is everything.
Intersections: locked candidates
The gentlest elimination uses the overlap between a box and a row or column. When all of a digit's candidates in a box sit on one line, or all of a line's candidates sit in one box, the digit is blocked elsewhere. Learn this one first; it appears constantly.
Groups: pairs and triples
When two or three cells reserve the same two or three digits between them, those digits are excluded from the rest of the house (naked sets), or the extra candidates are excluded from the reserving cells (hidden sets). These patterns are the workhorses of hard puzzles.
Fish patterns: X-Wing and Swordfish
Fish patterns follow a single digit across multiple rows and columns. X-Wing uses a 2x2 frame of candidate positions; Swordfish extends it to 3x3. Both eliminate the digit from the crossing lines and are the classic evil-level moves.
Wings: XY-Wing
XY-Wing (also called Y-Wing) builds a pivot-and-pincers triangle out of three bi-value cells. Whichever way the pivot resolves, one pincer takes the shared candidate, which can then be removed from every cell seeing both pincers.
The advanced syllabus at a glance
Work through the table in order. Each technique builds on the reading skills of the previous one; a solver who is fluent in pairs finds X-Wings much faster.
| Order | Technique | Builds on | What it teaches you |
|---|---|---|---|
| 1 | Locked candidates | Pencil marks | Reading box-line intersections; the simplest elimination, needed everywhere. |
| 2 | Naked pairs and triples | Locked candidates | Spotting cells that reserve digits inside a house. |
| 3 | Hidden pairs and triples | Naked pairs | Counting positions per digit instead of reading cell by cell. |
| 4 | X-Wing | Pairs | Following one digit across the whole grid; your first fish pattern. |
| 5 | Swordfish | X-Wing | Extending the fish logic from two lines to three. |
| 6 | XY-Wing | Pairs | Chaining bi-value cells: the doorway to every harder wing and chain. |
Frequently asked questions
Which advanced technique should I learn first?
Locked candidates. It is the easiest to spot, appears in almost every hard puzzle, and teaches the elimination mindset the other techniques rely on.
Do advanced techniques place digits?
No. They eliminate candidates. The placements come afterwards, when the eliminations reduce a cell or house to a single option.
Are there harder techniques than these?
Yes, such as chains and coloring, but they are rarely needed here. In the eight complete solves in our step-by-step guide, even the evil puzzles fall to singles, locked candidates, pairs and triples, and an occasional XY-Wing.
Practice next
Advanced patterns only become visible with mileage. Play hard and evil puzzles with full candidate discipline, and revisit each lesson when its pattern refuses to appear.