How to Play Sudoku: A Beginner's Guide with Tips (2026)

Some games hook you with speed and explosions. Sudoku does the opposite: it's quiet, it's patient, and it asks for nothing but a clear head and a little stubbornness. There's no timer breathing down your neck and no luck involved — just a grid, nine digits, and one elegant rule that unspools into hours of "ohhh, that's where the 7 goes." If you've ever glanced at a half-filled grid and felt locked out, this guide gets you in.

The one rule

Here's the whole game in a single sentence. A Sudoku is a 9×9 grid, divided into nine smaller 3×3 boxes, and your job is to fill every cell with a digit from 1 to 9 so that:

• each row of nine cells contains 1–9 with no repeats,
• each column of nine cells contains 1–9 with no repeats, and
• each 3×3 box contains 1–9 with no repeats.

That's it. Rows, columns, and boxes are the three kinds of "unit," and the same rule applies to all of them: every digit appears exactly once. The puzzle starts with some cells already filled in — those givens are your anchors — and a well-made Sudoku always has exactly one solution you can reach by logic alone.

Where to start: scanning

Don't stare at the empty cells. Stare at the digits.

The fastest opening move for a beginner is scanning (sometimes called cross-hatching). Pick a digit — say, 5 — and look across the grid for rows, columns, and boxes that already contain a 5. Because a 5 can't repeat in any unit, those existing 5s "block" entire rows and columns from holding another one.

Now zoom into a single 3×3 box that's still missing its 5. Cross off every cell in that box sitting in a row or column that already has a 5 elsewhere. If only one empty cell survives, that cell must be the 5 — there's nowhere else it can legally go. Place it, then keep scanning that same digit through the other boxes before moving to the next number. Early on, scanning alone will fill a surprising chunk of the grid.

Pencil marks: tracking candidates

Eventually scanning stops handing you free answers, and that's when pencil marks earn their keep. A pencil mark (or candidate) is a small note you make in an empty cell listing every digit that's still legal there — that is, not already present in its row, its column, or its box.

Go cell by cell and jot the surviving candidates. A cell that could still be a 2, 5, or 8 gets a tiny "2 5 8." This converts the puzzle from "what goes here?" into something far more mechanical: every time you place a digit, you sweep through the cells that share its row, column, and box and erase that digit from their candidate lists. Keeping pencil marks honest and up to date is the single biggest habit separating a stuck beginner from a steady solver.

Solving techniques

With candidates in place, two reliable patterns will carry you through most beginner and intermediate puzzles.

Naked singles. Watch for any cell whose candidate list has shrunk to exactly one digit. If a cell can only legally be a 4, then it is a 4 — no other option exists. Place it, erase 4 from its neighbours' candidates, and often that triggers another naked single. These chain together beautifully.

Hidden singles. This one is sneakier and a bit more powerful. Look at a single unit — one row, column, or box — and check each digit 1–9. If a digit appears as a candidate in only one cell of that unit, it belongs there, even if that cell still lists other candidates too. The other digits are pretenders; this is the only home that digit has in the unit, so it wins. Hidden singles are exactly what scanning finds, just spotted through your candidate marks instead of by eye.

Underneath both moves is the same engine: eliminating candidates. Every placement removes possibilities elsewhere, and removing possibilities reveals the next forced placement. Work the loop — place, eliminate, rescan — and the grid fills itself.

Common mistakes

A few habits trip up almost every beginner:

• Guessing. Never do it. Sudoku is pure logic; if no move is obvious, you've missed a deduction, not run out of luck. A guess that "feels right" can quietly poison the whole grid.
• Sloppy pencil marks. Forgetting to erase a candidate after a placement leads you to "deduce" something false. Update candidates every single time you write a digit.
• Tunnel vision on one box. If a box stalls, switch units — work a row or a column, or scan a different digit. Fresh angles break logjams.
• Ignoring columns. Beginners scan rows and boxes but forget the column constraint is just as strong. Check all three units for every move.

Ready to solve?

The beautiful thing about Sudoku is that it never lies to you: every grid is solvable by reasoning, one forced move at a time. Master scanning, keep clean pencil marks, and learn to spot naked and hidden singles, and you'll go from locked out to logically unstoppable.

Time to put it to work. Open Sudoku, start with the digit that already appears the most, and scan your way in. When you're ready for your next puzzle fix, the rest of the games library is one click away.