Sudoku techniques form a ladder, and climbing it in the right order matters more than most beginners realize. Each technique builds on the perceptual habits of the one before it: you cannot reliably spot a Hidden Pair until scanning for Hidden Singles is automatic, and an X-Wing is nearly invisible until you are comfortable tracking a single digit across the whole grid. This guide lays out the standard progression, explains why it is ordered the way it is, and tells you how to know when you are ready for the next rung.
The ladder at a glance
- Naked Single — one candidate left in a cell
- Hidden Single — one home left for a digit in a unit
- Omission (Locked Candidates) — box–line intersections
- Naked Pair and Hidden Pair
- Naked Triplet and Hidden Triplet
- Naked Quad and Hidden Quad
- X-Wing — the first two-unit pattern
- Swordfish — the three-unit generalization
There is a logic to this order beyond tradition. Stages 1–2 place digits. Stages 3–8 only eliminate candidates, which then feed new singles. And the pattern size grows steadily: one cell, one intersection, two cells, three, four, then patterns spanning multiple rows and columns. Each stage enlarges the amount of the grid you must hold in view at once — that is the real skill being trained.
Stage 1: The singles (your first week)
A Naked Single is a cell with only one possible digit remaining; a Hidden Single is a digit with only one possible cell remaining in some row, column, or box. They are two views of the same fact — cells need digits, digits need cells — and together they solve every easy puzzle ever printed.
The critical habit to build here is the loop: every time you place a digit, immediately re-examine the cells it touches, because each placement tends to create the next single. Chains of five or six consecutive singles are common. Solvers who scan the grid randomly instead of following the consequences of their last placement waste most of their effort. Our guide to scanning and cross-hatching covers the eye movements in detail.
Ready to move on when: you can finish an easy puzzle without pencil marks, and singles feel like reading rather than searching.
Stage 2: Omission (the most undervalued technique)
Omission — also called Locked Candidates, Pointing, or Box–Line Reduction — fires when all of a digit's possible cells in a box fall on one row or column (or vice versa). The digit is trapped on that line inside that box, so it can be eliminated from the rest of the line (or the rest of the box).
Learners often skip past Omission to get to the glamorous pairs and triples. That is a mistake. Omission is the highest-frequency elimination technique in medium puzzles, it requires no pencil marks to spot, and it teaches the box–line geometry that every later technique leans on. Master it before anything else that eliminates.
Ready to move on when: you routinely notice pointing pairs during your normal digit scan, without hunting for them deliberately.
Stage 3: Pairs, then triples, then quads
The subset techniques all rest on one principle: if k digits are confined to k cells of a unit, those cells belong to those digits and everything else clears away. (The full logic, including why naked and hidden subsets are mirror images of each other, is in Why Naked and Hidden Subsets Work.)
Learn them in size order, naked before hidden at each size. Naked Pairs are visually obvious once you keep pencil marks — two cells showing the same two candidates. Hidden Pairs require per-digit bookkeeping and come slower. Triples add a wrinkle that trips up almost everyone at first: the three cells need not each contain all three digits — the union of their candidates just has to be exactly three digits. A cell showing only two of the three still counts.
Quads are rare in practice; learn the pattern, but do not expect to use it often. This is also the stage where disciplined pencil marks become mandatory — subset techniques operate on candidates, so sloppy candidates mean missed and false patterns alike.
Ready to move on when: given a fully pencil-marked grid, you can find a planted pair or triple in under a minute, and you no longer see “false triples” (three cells whose candidates span four digits).
Stage 4: The fish — X-Wing and Swordfish
Everything before this stage happens inside a single unit. The fish patterns are the jump to reasoning across units: an X-Wing traps a digit in two cells in each of two rows, aligned on the same two columns, which pins the digit to those columns and clears it from every other row. A Swordfish does the same with three rows and three columns. The family logic — and where the odd names came from — is covered in The Fish Family Explained.
The prerequisite skill is single-digit vision: the ability to look at the grid and see only, say, the 7s — where they are placed, where they remain possible. If that feels hard, practice it directly for a few puzzles before attempting X-Wings.
Ready to move on when: you find X-Wings without being told one exists. That is the honest test, and it is exactly what this site is built for.
Why practicing one technique at a time works
There is a well-known trap in Sudoku learning: you read about a technique, nod along, and then never use it, because in a random puzzle you cannot tell which technique is needed when you get stuck. The pattern-recognition literature is clear that recognition is built by repeated exposure with feedback — seeing the same pattern many times in varied positions, with confirmation that you got it right.
That is the idea behind Precision Sudoku's technique picker: you choose exactly which techniques a puzzle should require, and the generator guarantees the puzzle needs them — no more, no less. Drilling ten X-Wing puzzles in a row does more for your X-Wing vision than a month of random puzzles. Once a technique feels automatic in isolation, mix it back in with everything below it on the ladder, then move up a rung.
What comes after Swordfish?
Beyond this site's ladder lie Jellyfish (four-row fish), finned and sashimi fish variants, XY-Wings, uniqueness-based techniques (see our uniqueness guide), coloring, and eventually full chain logic. The good news: the jump from Swordfish to those is smaller than the jump from singles to Swordfish. By the time you are here, you have learned how to learn a pattern — the rest is vocabulary.