How to Play Sudoku: Strategy, Tips & Free Daily Puzzles

By Ramkrishna Prasad · Updated October 8, 2026

Sudoku is the most-played logic puzzle on the planet, and also one of the most misunderstood. The rules take about thirty seconds to learn, yet the same grid that traps a beginner is finished by an experienced solver in a smooth, guess-free flow. The gap is not intelligence or memory — it is a small set of habits applied in the right order. This guide shows you how to play Sudoku from the very first square to the patterns that crack expert grids, and hands you a sudoku strategy you can reuse every single day.

If you would rather learn by doing, open our free Sudoku online in a second tab and follow along as you read.

What Is Sudoku? The Rules in Thirty Seconds

A standard Sudoku is a 9×9 grid divided into nine 3×3 boxes. Some cells already contain a digit — these are the "givens." Your job is to fill every empty cell with a digit from 1 to 9 so that:

• every row contains each digit exactly once,
• every column contains each digit exactly once, and
• every 3×3 box contains each digit exactly once.

Those three rules run in every direction, which gives 27 units in total — nine rows, nine columns and nine boxes — each of which must hold 1 through 9 without repeats. That is the entire ruleset. No sums, no order of operations, no trick questions. A well-built puzzle has a single valid solution, so you can always reach the answer by deduction rather than by trial and error.

Sudoku Has Nothing to Do With Maths

People bounce off Sudoku because the digits look like sums. They are not. In Sudoku, 7 is just a symbol, no different from a letter or a color. You never add anything, and you never count beyond nine. What you are actually doing is tracking constraints: because a digit already sits in this row, it cannot sit anywhere else in that row. Children and adults who "hate maths" often turn out to be excellent solvers, because the real skill is pattern-spotting, not calculation.

Sudoku Strategy Starts With Scanning One Digit at a Time

A sudoku strategy is simply an ordered set of habits, and the first habit — the one that solves more puzzles than every advanced technique combined — is scanning. Pick a single digit, say 4, and sweep the grid box by box. In each 3×3 box ask: where can a 4 legally go? Cross out any cell whose row or column already holds a 4, and you will often find that only one square in the box survives. That square must be the 4.

That discovery has a name: a hidden single. It is "hidden" because the cell's candidate list may still show several options — the 4 is forced by the rows, columns and boxes around it, not by what is written inside the cell.

Worked example. Look at the middle box. Rows 4, 5 and 6 pass through it, and columns 4, 5 and 6 pass through it. Suppose the givens put a 4 in row 4 somewhere to the left of the box, and another 4 in column 6 somewhere below it. Every cell in row 4 and every cell in column 6 is now illegal for 4. If the box's other cells are already filled, and only one empty cell escapes both of those lines, that cell must be the 4 — placed in seconds, with no erasing and no guessing.

The habit that separates fast solvers from slow ones is scanning the same digit across all nine boxes before moving to the next digit. Chasing one cell feels productive, but a full sweep plants several digits at once, and each new digit eliminates more candidates for the rest of the grid.

How to Use Pencil Marks Without Cluttering the Grid

When scanning stalls, pencil marks come out. In an empty cell you note every digit that could still legally go there, usually in tiny writing in a corner. The goal is not to mark everything — it is to shrink the grid until your eye can read it.

• Mark the crowded cells first. A cell with two or three candidates is where pairs and triples hide; a cell with seven is noise.
• Work one unit at a time. Finish a row, then a box, so you always know where you stopped.
• Erase as you place. The moment a digit lands, remove it from every cell in the same row, column and box.
• Keep notation consistent. Same corner, same order, every time — your memory will thank you.

Candidates are the foundation for every technique below. If you want the full walkthrough of building and cleaning up a candidate grid, our Sudoku tips and strategies page covers it step by step.

Sudoku Techniques, From Easy to Expert

Once candidates are on the page, the following patterns cover almost every puzzle you will meet. Learn them in this order and you will climb difficulty levels without ever guessing.

• Naked single: a cell whose candidate list has shrunk to one digit. Fill it immediately — it is a free square.
• Hidden single: a digit that fits only one cell in a unit, even though that cell still shows other candidates. This is the scanning find you already know.
• Naked pair: two cells in the same row, column or box that share the same two candidates (say 3 and 8). Those two digits must occupy those two cells, so erase 3 and 8 from every other cell in that unit.
• Hidden pair: the mirror image. Two digits that can only fit in the same two cells of a unit, so those cells must be those digits and you can erase all their other candidates.
• Pointing pair (box-line reduction): if a candidate inside a box can only appear in one row or column of that box, the digit must lie on that line — remove it from the rest of the row or column outside the box.
• Claiming (line-box reduction): the reverse. If a candidate in a row or column can only appear inside a single box, remove it from the rest of that box.
• X-Wing: the first pattern that needs two units at once, described in its own section below.

Worked example (naked pair). In one box, two cells each show exactly the candidates 3 and 8 and nothing else. Those two digits have to occupy those two cells between them — there is no room for either to go anywhere else in the box. So every other cell in the box can safely drop 3 and 8. The same logic works when the two cells share a row or a column instead of a box.

When you spot a pair, do not just note it — erase the redundant candidates straight away, because tidying candidates is what keeps the grid solvable.

X-Wing: The First Advanced Technique

X-Wing appears when a digit has exactly two candidate cells in each of two different rows, and those four cells sit in the same two columns. Picture the four cells as the corners of a rectangle. The digit must occupy one diagonal or the other — never all four corners — and whichever diagonal it lands on, both of those columns already contain the digit. That means you can erase it from every other cell in those two columns.

The pattern also runs rotated: find two columns whose candidates for a digit share two rows, and you can clear that digit from the rest of those two rows. X-Wing is the first technique that forces you to compare two units at once, which is exactly why it usually appears only at hard and expert level. If it sounds abstract, do not worry — you will rarely meet it before you have mastered everything above it.

A Repeatable Solving Order (So You Never Stall)

Advanced techniques are not hard because they are complicated; they are hard because beginners reach for them while an easy single is still sitting on the board. Work in this order instead:

1. Scan the givens for naked singles and fill them.
2. Run a full 1-through-9 sweep for hidden singles.
3. Add pencil marks where candidates have thinned out.
4. Re-scan after every placement — a new digit often creates a new single two boxes away.
5. Hunt naked and hidden pairs, then erase the candidates they eliminate.
6. Apply pointing and claiming to force digits out of boxes.
7. Only then reach for X-Wing.

The discipline of re-scanning is what makes this order work. Most "stuck" grids are not stuck at all; they simply have a fresh single that appeared after the last digit you placed.

Sudoku Tips: Five Beginner Mistakes That Cost You Time

1. Guessing. A digit filled by luck trains nothing and can dead-end the grid. If you feel the urge to guess, there is a technique you have not used yet.
2. Refusing pencil marks. Holding every candidate in your head works up to medium and collapses at hard. Write them down.
3. Scanning only rows. Always scan both directions and the boxes too. Most hidden singles hide in box-to-line eliminations.
4. Ignoring the boxes. Newer solvers treat Sudoku as rows and columns and forget the 3×3 rule, which is where the strongest constraints live.
5. Erasing without a reason. Every removed candidate should trace back to a placed digit or a pattern. If you cannot say why, restore it.

How Hard Is Each Difficulty, Really?

Difficulty is not about how many givens a puzzle starts with — it is about which techniques the puzzle forces you to use. A grid with few givens but an obvious solution can be easier than one that looks busy and hides a pointing pair.

So do not judge a puzzle by its first glance — judge it by whether a full sweep finishes it. When you get stuck, the Sudoku solver will name the next logical step without spoiling the whole grid, which is a far better teacher than a reveal.

Why a Free Daily Sudoku Beats Occasional Grinding

Technique only sticks with repetition, and repetition is exactly what a daily puzzle gives you. Because each day's grid is generated from the date, everyone everywhere plays the same Sudoku on the same day. That single design choice changes how the puzzle feels: your time is directly comparable to other solvers, a finish is worth sharing, and a streak becomes a small, honest measure of consistency. Five minutes a day teaches pattern recognition far faster than a ninety-minute session every other weekend.

It is also genuinely a free daily sudoku — one shared board, no paywall, and a clean stop when the grid is done. Compare your time on the daily leaderboard, then use the puzzle as a warm-up before exploring the number games and logic puzzles hubs.

Sudoku Variants and Puzzle Cousins

Once the classic 9×9 feels comfortable, the same deduction muscle shows up in neighbouring puzzles. Nonogram, also called Picross, makes you infer filled cells from row and column counts — pure logic with no digits at all. Minesweeper is deduction under uncertainty, and it trains you to reason about what a tile would imply before you click it. If you want the same daily Sudoku with no distractions around it, Sudoku Unblocked runs the classic grid on a clean page. And when you feel like switching from digits to letters, the word games hub is the place to start.

Play Today's Free Sudoku

Ready to put this into practice? Play our free daily Sudoku — pick easy, medium, hard or expert, use hints if you must, and post your time to the daily Top 50. The puzzle resets at midnight US Eastern, the same for everyone.