Hard Sudoku Puzzles
Challenge your brain with these free printable hard Sudoku puzzles. Sharpen your mind with these simple and fun brain teasers. Download, print and enjoy hours of addictive puzzle-solving fun.
12x12 Sudoku - Hard - 10
9x9 Sudoku - Hard - 1
9x9 Sudoku - Hard - 20
9x9 Sudoku - Hard - 19
6x6 Sudoku - Hard - 2
9x9 Sudoku - Hard - 10
9x9 Sudoku - Hard - 9
9x9 Sudoku - Hard - 8
9x9 Sudoku - Hard - 7
9x9 Sudoku - Hard - 6
9x9 Sudoku - Hard - 5
9x9 Sudoku - Hard - 4
9x9 Sudoku - Hard - 3
9x9 Sudoku - Hard - 2
9x9 Sudoku - Hard - 11
About Classic Sudoku Puzzles
Sudoku is a logic-based, popular number-placement puzzle. The classic Sudoku grid consists of a 9×9 board divided into nine 3×3 sub-grids called "boxes" or "regions." The goal is to fill the grid with digits from 1 to 9 so that each digit appears exactly once in each row, column, and box.
Sudoku puzzles vary in difficulty, ranging from easy to expert, depending on how many digits are pre-filled and the complexity of solving them.
Basic Rules / How to Play
- Grid Size: The puzzle has typically 9x9 grid size made up of three 3x3 sub-grids. The other variation can be of 4x4, 6x6, 10x10, 16x16 etc.
- Rows: Each row must contain all digits from 1 to 9. No digit can be repeated within a single row.
- Columns: Each column must contain all digits from 1 to 9. No digit can be repeated within a single column.
- Box: Each 3×3 box must contain all digits from 1 to 9. No digit can be repeated within any of the nine 3×3 subgrids.
- Pre-Filled Numbers: The numbers given at the start of the puzzle must remain unchanged.
Solving Tips and Techniques:
- Most Pre-filled Numbers: Start with rows, columns, or boxes with the most pre-filled numbers.
- Scanning: Look for empty cells where only one number is possible based on the existing numbers in the row, column, and 3x3 subgrid.
- Elimination: If a number can only go into one cell in a row, column, or box, place it there.
- Single Candidates: A cell that can only have one number is filled right away.
- Candidate Lists: Write all the possible numbers in each empty cell. As you fill in numbers, remove the ones that no longer work.
- Naked Pairs / Triples: If two (or three) cells in a row, column, or box can only have the same two (or three) numbers, remove those numbers from the other cells in that row, column, or box.
- Hidden Pairs / Triples: Find numbers that show up in only two or three cells in a row, column, or box, even if there are other possible numbers too.
- Guess and Backtrack: For very challenging puzzles, guess a number and follow through to see if it leads to a valid solution. If not, backtrack and try another possibility.
- Use pencil and paper: Use pencil marks to keep track of possible numbers in each cell
