Sudoku: Start with What Is Missing
Sudoku is a constraint puzzle. Every cell must agree with its row, column and box at the same time. Guessing early often creates contradictions that are difficult to trace.
Begin with crowded groups
Look for a row, column or 3×3 box that already contains many digits. List the missing numbers. For each empty cell, eliminate values that already appear in its row and column.
Two ways to find a single
A cell can have only one possible digit after you compare all three groups. Alternatively, a missing digit may have only one possible position within a group. Both are useful deductions, even when several other cells remain uncertain.
Check without assuming a solution
GameHub’s Check grid button highlights current repeated-number conflicts. No conflict does not mean every choice is necessarily part of a completed solution. Continue checking how values restrict nearby cells.
About generated boards
Our boards are created by removing entries from a valid completed grid. They may permit more than one solution. The game accepts a fully filled grid whenever all row, column and box rules are satisfied.
Use mistakes constructively
If a conflict appears, erase a doubtful entry and work through the nearby group again. Restart when you want a fresh board rather than trying to preserve a guess you no longer trust.