Sudoku solving techniques form a ladder. Each rung is a pattern you can learn in a few minutes, and each one unlocks puzzles the previous rungs could not crack. This page lists all 37 techniques we use, from the singles every beginner knows to the forcing nets behind our hardest Killer puzzles, in the order a solver actually needs them.
Classic and Killer Sudoku share most of the ladder. Killer adds nine cage-based techniques of its own, marked below. If you play only classic puzzles, skip the Killer entries; everything else applies to both.
Work from the top down. When you are stuck, the technique you need is almost always the simplest one you have not tried yet, not the fanciest one you know.
The stall loop, in order:
singles -> pairs / triples -> pointing pairs, box line reduction
-> cage arithmetic (Killer only)
-> wings and fish
-> chains and colouring
-> almost locked sets, forcing nets
-> last resort
Drop back to the top after every placement.
| Tier | What it adds | Where you meet it |
|---|---|---|
| Basic | Counting candidates inside one unit | Easy, Medium |
| Tough | Patterns across two or three units, cage arithmetic | Hard |
| Diabolical | Chains of linked candidates | Expert |
| Extreme | Grouped links, almost locked sets, nets | Master, Legendary |
| Last resort | Guess and verify | Anything left over |
Thirty-seven techniques in complexity order. Filter to the mode you play, or read straight down — every article links to the next rung.
Every technique page ends with the difficulty level where the pattern first becomes necessary, so you can pick a matching puzzle and try it immediately. Start with easy Killer Sudoku for the cage basics, or hard classic Sudoku for wings and fish.