Board structure
The board consists of 9 rows, 9 columns and 9 small 3x3 square blocks.
Sudoku
Classic number puzzle Sudoku for logic training and focus.
How to play
Basic rules of classic 9x9 Sudoku.
Placement conditions
Each row, column and 3x3 block must contain digits from 1 to 9 exactly once without repeats.
Initial clues
Some numbers are pre-filled as initial clues and cannot be modified. Your goal is to fill all remaining empty cells.
Tips and strategies
Standard techniques and best practices for quick and accurate puzzle solving.
1. Cross-hatching rows and columns
Find a number that already appears frequently across the board. Trace lines across rows and columns where it is placed to eliminate lines in adjacent 3x3 blocks and isolate the remaining empty cell.
2. Naked single
Inspect a specific empty cell and check all numbers already present in its row, column and 3x3 box. If eight out of nine digits are eliminated, only one valid choice remains.
3. Filled sectors
Start solving from rows, columns or 3x3 boxes that already have the most cells filled (such as 6 or 7). Finding the 2 or 3 missing digits in such sectors is much easier.
4. Hidden single
Check which cells inside a single 3x3 block can accommodate a specific required number. If only one cell can hold that number, place it there.