Sudoku looks like a numbers game, but it's really a logic game that happens to use digits 1–9. Whether you're stuck on your first puzzle or looking to finally crack "hard" difficulty, here's a full progression of Sudoku techniques - from the basics to genuinely advanced strategies.
Beginner techniques
Scanning (row, column, box elimination). The foundational technique: for any empty cell, look at its row, column, and 3x3 box together. Any number already present in any of those three eliminates that number as a possibility for the empty cell. Once only one number is left, you've solved that cell.
Single candidate (naked single). If, after scanning, a cell has only one possible number left, that number must go there. This is the simplest possible solving step and usually how most puzzles start.
Hidden single. Sometimes a number can only go in one place within a row, column, or box - even if that cell looks like it has multiple candidates at first glance. If you check where a specific number (say, 7) could legally go within a box, and only one cell allows it, that's a hidden single.
Intermediate techniques
Pointing pairs / pointing triples. If a number's only possible cells within a box all fall in the same row or column, that number can be eliminated from the rest of that row or column outside the box - even before you know exactly which of those cells it belongs in.
Naked pairs / naked triples. If two cells in the same row, column, or box share the exact same two candidate numbers (and no others), those two numbers must occupy those two cells - meaning you can eliminate both numbers as candidates from every other cell in that row, column, or box.
Hidden pairs / hidden triples. The reverse of a naked pair: if two numbers can only go in the same two cells within a unit - even if those cells have other candidates too - those two numbers are "locked" to those cells, letting you eliminate their other candidates.
Advanced techniques
X-Wing. When a candidate number appears in exactly two cells in each of two different rows, and those cells align in the same two columns, you can eliminate that candidate from the rest of those columns. It's a pattern that looks like an "X" across the grid - hence the name.
Swordfish. An extension of X-Wing across three rows and three columns instead of two - rarer, but works on the same underlying logic: if a candidate's possible positions are constrained to the same set of columns across three rows, it can be eliminated elsewhere in those columns.
Colouring. A technique where you mentally (or literally, with two colours) track a candidate's possible chains of placement across the grid, looking for contradictions that eliminate entire chains at once. This is typically reserved for the hardest puzzle difficulties.
A simple progression to follow
Scan for naked and hidden singles first - always. Move to pointing pairs and naked/hidden pairs when you get stuck. Only reach for X-Wing, Swordfish, or colouring on genuinely hard puzzles - most everyday Sudoku doesn't need them.
Practice makes it click
Like any logic skill, Sudoku technique is best learned by doing, not just reading. Play today's Sudoku and try spotting a naked pair or pointing pair in the wild.
Frequently asked questions
What's the easiest Sudoku technique to learn first?
Scanning - checking each empty cell against its row, column, and box to rule out numbers already used - is the foundation everything else builds on.
What's the difference between a naked pair and a hidden pair?
A naked pair is two cells that each have only the same two candidates left; a hidden pair is two candidates that only appear in the same two cells, even if those cells still have other candidates pencilled in.
Do I need to know X-Wing or Swordfish to solve most Sudoku puzzles?
No - most everyday Sudoku, including hard grids, can be solved with scanning and the pair-based techniques. X-Wing, Swordfish, and colouring are reserved for genuinely tough puzzles.
Ready to spot these in the wild? Play today's Sudoku.