How to Win at Sudoku: A Beginner's Guide
Sudoku is a pure logic puzzle — no math required, despite all the numbers. You get a 9×9 grid split into nine 3×3 boxes, partly filled with digits. Your job is to fill every empty cell so that each row, each column, and each 3×3 box contains the digits 1 through 9 exactly once, with no repeats. A well-made puzzle has exactly one solution, and you can always reach it with reasoning alone. Never guess.
The one rule that matters
- Every row must hold 1–9 with no repeats.
- Every column must hold 1–9 with no repeats.
- Every 3×3 box must hold 1–9 with no repeats.
If you can find a cell where a digit is forced by these three constraints, you've made progress. The whole game is finding forced cells, one after another.
Start by scanning
Scanning is the fastest beginner technique and needs no notes.
- Pick a digit, say 5, and look across the board for where 5s already appear.
- For each 3×3 box that has no 5, cross out every row and column that already contains a 5.
- If only one cell in that box survives, it must be a 5. Fill it in.
- Repeat for the digits that appear most often first — they give the most eliminations.
Naked singles and hidden singles
These two ideas will solve most easy and medium puzzles.
- Naked single: a cell where eight of the nine digits are already blocked by its row, column, and box. Only one digit can go there, so place it.
- Hidden single: within a single row, column, or box, a digit that can legally fit in only one cell — even if that cell could theoretically take other digits. It's "hidden" because you find it by looking at the digit, not the cell.
Use pencil marks
When scanning stops producing answers, write small candidate notes (the digits still possible) in each empty cell. Good candidate lists unlock more advanced logic.
- Naked pair: if two cells in the same unit both show only the same two candidates, those two digits are locked to those cells. Remove them from every other cell in that unit.
- Pointing pairs: if a digit's only candidates in a box all sit in one row (or column), that digit can be erased from the rest of that row (or column) outside the box.
Habits that prevent mistakes
- Fill only what you can prove. A single guess that's wrong can wreck an entire grid and force a restart.
- Update your notes every time you place a digit — erase it from the row, column, and box.
- Work the most-filled areas first. Boxes and rows that are nearly complete are where forced cells hide.
- Take a break if you stall. Fresh eyes catch a hidden single you scanned right past.
The satisfying part of Sudoku is that steady logic always wins — there's no luck, no dead end you can't reason your way out of.
Play Sudoku free and try scanning your first puzzle. Once you're hooked on number logic, the cross-sums puzzle Kakuro and the deduction grid of Nonogram make great next steps.
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