How to Solve Sudoku: Techniques from Beginner to Expert

Every Sudoku puzzle can be solved by pure deduction — no guessing, no trial and error. The trick is knowing which technique to reach for at each stage. This guide walks through the toolkit roughly in the order you’ll need it, from the scanning you’ll do on your very first puzzle to the pattern recognition that cracks the hardest ones.

If you haven’t played yet, the Sudoku board is a good place to try these techniques as you read.

The rules, briefly

A Sudoku grid is 9x9, divided into nine 3x3 boxes. Every row, every column, and every box must contain the digits 1 through 9 exactly once. That’s the entire rule set — everything else is a consequence of it. Because each digit can appear only once per row, column, and box, filling in one cell often eliminates possibilities elsewhere, and a full solve is just a chain of those eliminations.

Scanning: your first and most-used technique

Scanning means picking a digit — say, 7 — and checking each box to see if its position is forced. Look at a box that doesn’t yet contain a 7. Trace the rows and columns that already have a 7 in them; those rows and columns are eliminated within the box. If that leaves only one open cell, the 7 goes there.

Scanning gets more powerful as the grid fills in, because more rows and columns get “locked out” by existing digits. On an easy puzzle, scanning alone can often solve the whole board. It’s also the fastest technique to do in your head, so even on harder puzzles it’s worth a scanning pass before reaching for anything more elaborate.

Naked singles

A naked single is a cell that has only one possible candidate left, once you account for every digit already present in its row, column, and box. If you’re tracking candidates with pencil marks (or the notes feature in-game), a naked single is simply a cell where only one note remains after your other deductions have eliminated the rest.

This is the most mechanical technique in Sudoku — it doesn’t require insight, just bookkeeping. Whenever you place a digit, it’s worth rechecking the cells in its row, column, and box for new naked singles, since removing one candidate can cascade into several more.

Hidden singles

A hidden single is subtler: it’s a cell where a digit is the only place that digit can go within a row, column, or box, even though the cell itself still shows multiple candidates. For example, if a box has three empty cells and only one of them can legally hold a 4 (because the other two are blocked by a 4 elsewhere in their row or column), that cell is a hidden single for 4 — regardless of how many other candidates it appears to have.

Hidden singles are easy to miss if you’re only scanning cells for their candidate count, because the cell doesn’t look “obviously” solved. Instead, scan digit by digit within each unit (row, column, box) and ask, “where can this digit still go?” If the answer is one cell, you’ve found it.

Pointing pairs and pointing triples

Once naked and hidden singles are exhausted, look for pointing pairs. If, within a single box, the candidates for a digit are confined to just two or three cells that all sit in the same row or column, that digit can be eliminated from the rest of that row or column outside the box. The box “points” its candidate positions outward and rules out that digit elsewhere on the line.

This technique doesn’t solve a cell by itself, but it prunes candidates, which often unlocks a naked or hidden single somewhere else on that row or column. It’s the first technique that requires actually looking at candidate positions rather than counts, which is why it usually marks the jump from easy to medium difficulty.

Naked pairs and triples

If two cells in the same unit share exactly the same two candidates (and no others), those two digits must occupy those two cells in some order — you don’t know which, but you know no other cell in that unit can hold either digit. That lets you strip both candidates from every other cell in the unit.

The same idea extends to naked triples: three cells whose combined candidates span only three digits total (even if no single cell has all three) form a triple, and those three digits can be eliminated from the rest of the unit. Spotting these requires actually comparing candidate lists across cells, which is where a notes/pencil-mark system starts to earn its keep.

X-wing: your first “advanced” pattern

X-wing is usually the first technique that feels like a genuine “aha.” Pick a digit and look across the whole grid: if that digit’s candidates in two different rows are confined to exactly the same two columns, those four cells form a rectangle — an X-wing. Because each of those two rows must place the digit in one of those two columns, the digit can be eliminated from every other cell in those two columns.

X-wing only shows up on genuinely hard puzzles, and it requires tracking one digit across the entire board rather than within a single unit. If you’re pencil-marking, it helps to isolate one digit at a time and scan just for it across all nine rows.

Working difficulty up gradually

The techniques above roughly track difficulty tiers: easy puzzles usually fall to scanning and naked singles; medium puzzles add hidden singles and pointing pairs; hard puzzles need naked pairs/triples and eventually X-wings. If you get stuck, it’s almost always because a technique from the next tier up is needed, not because you made an error — so it’s worth deliberately re-scanning for the next pattern rather than staring at the same cells.

For a broader look at what puzzles like this actually train (and what they don’t), see how logic puzzles sharpen problem-solving. And if you want Sudoku as part of a regular routine rather than a one-off, the Daily Puzzle rotates it in along with six other games.