A fully playable Sudoku puzzle in your browser. No app, no account, no pencil.
The Sudoku game at Ultimate Tools generates fresh puzzles on every game — built in React, three difficulty levels, with hint support and error checking.
How to Play Sudoku
Goal: Fill the 9×9 grid so that every row, every column, and every 3×3 box contains all digits from 1 to 9 exactly once.
Rules:
- No digit can repeat in the same row
- No digit can repeat in the same column
- No digit can repeat in the same 3×3 box
- Every puzzle has exactly one valid solution
Controls:
| Action | How |
|---|---|
| Select a cell | Click the cell |
| Enter a digit | Press 1–9 on keyboard |
| Clear a cell | Press Backspace or Delete |
| Get a hint | Click Hint button |
| Check errors | Click Check button |
| New puzzle | Click New Game |
Difficulty Levels
| Level | Cells revealed | What it means |
|---|---|---|
| Easy | ~45–50 | More given digits, fewer deductions needed |
| Medium | ~35–40 | Requires multi-step logic |
| Hard | ~25–30 | Sparse givens, advanced techniques required |
Start on Easy to learn the logic. Hard puzzles may require techniques like X-wings or forcing chains.
Core Solving Techniques
Single candidate: If a cell can only hold one digit (all others are already in its row, column, or box), fill it in.
Hidden single: If a digit can only go in one cell within a row, column, or box — even if that cell has other possibilities — place it there.
Elimination: For each empty cell, list which digits are still possible. Cross out candidates that already appear in the same row, column, or box. Narrow it down.
Box-row/column interaction: If a digit in a 3×3 box can only appear in one row or column within that box, you can eliminate that digit from the rest of that row or column outside the box.
Tips
Use pencil marks (mental or on paper). Before committing to a digit, note the candidates for each cell. This makes eliminations visible.
Work the easy cells first. Filling obvious singles creates new constraints that open up more singles. The puzzle cascades.
Don't guess on Easy or Medium. Every Sudoku puzzle is logically solvable — guessing isn't necessary. If you're guessing, there's a deduction you haven't found yet.
Use the Hint sparingly. Hints reveal one correct digit. Use them when stuck, not as a shortcut — the satisfaction of solving it yourself is the point.
No Download, No Account
Each puzzle is generated fresh in your browser. Built in React. Nothing installed, no progress saved.
Play Sudoku at Ultimate Tools.
Other Games at Ultimate Tools
- Minesweeper — logic-based mine detection
- Solitaire — classic Klondike card game
- Memory Game — flip and match pairs
- Snake — grow the snake, avoid the walls
- Brick Breaker — clear bricks with a ball and paddle
- Typing Speed Test — measure your WPM
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