What is Sudoku?

Sudoku is a logic-based number puzzle that originated in Japan and has become one of the world's most popular brain games. The puzzle consists of a 9×9 grid divided into nine 3×3 boxes (also called regions or blocks). The objective is simple: fill in the grid so that every row, column, and 3×3 box contains all digits from 1 to 9 exactly once, with no repetition.

Unlike crosswords or trivia games, Sudoku requires no mathematical calculations or specialized knowledge—just pure logical deduction. Players analyze the given numbers (called "clues" or "givens") and systematically determine where each missing number must go based on the rules of elimination.

How does Sudoku difficulty work?

Sudoku puzzles are rated by difficulty based on the solving techniques required rather than simply the number of given clues. Easy puzzles can typically be solved using basic elimination—looking at a row, column, or box and determining which numbers are missing. Medium puzzles require more advanced techniques like naked pairs or hidden singles.

Hard and expert puzzles demand sophisticated strategies such as X-Wing, Swordfish, or chain-based logic where you must track multiple possibilities across the grid. The difficulty rating in this generator uses an algorithm that analyzes the puzzle structure to estimate the complexity of techniques needed to reach the solution.

Tool description

This Sudoku Generator creates random, valid Sudoku puzzles with guaranteed unique solutions across four difficulty levels. Each generated puzzle comes with its complete solution, statistics about the puzzle composition, and a print-friendly option for offline solving.

The generator uses a sophisticated algorithm that first creates a complete valid Sudoku grid, then strategically removes numbers while ensuring the puzzle maintains exactly one solution. The difficulty is controlled by analyzing the solving complexity required for each generated puzzle.

Features

  • Four difficulty levels: Easy, Medium, Hard, and Expert puzzles tailored to different skill levels
  • Instant puzzle generation: Creates new unique puzzles with a single click
  • Solution toggle: View or hide the complete solution at any time
  • Puzzle statistics: Displays the count of given numbers and empty cells
  • Print functionality: Clean, printer-friendly output for solving puzzles on paper

Use cases

  • Daily brain training: Generate a fresh puzzle each morning to keep your mind sharp and improve logical thinking skills
  • Teaching logic to students: Educators can create puzzles of appropriate difficulty for classroom activities or homework assignments
  • Offline entertainment: Print puzzles for travel, waiting rooms, or screen-free relaxation time
  • Puzzle competition preparation: Practice with expert-level puzzles to prepare for Sudoku tournaments or timed challenges