Compare candidates by unit
Look for two cells in a row, column, or box that share the same two candidates. That pair removes those digits from other cells in the unit.
Hard Sudoku Online
Hard Sudoku reduces the obvious moves and rewards careful candidate management, pattern recognition, and patient deduction.
What makes a Hard Sudoku?
Hard puzzles on Sudoku Hot begin with about 26 given digits. Clue count is only a guide: the real difficulty comes from how those givens interact and which techniques unlock the next placement.
You may need locked candidates, naked or hidden pairs, and repeated passes through the grid. Each move should still follow from logic; a sparse-looking board is not an invitation to guess.
Solving tips
Use box-line interactions
When a digit inside a 3×3 box is limited to one row or column, eliminate that digit from the rest of the same line.
Audit before using a hint
Recheck recent placements and notes. A missed elimination is more common than a genuinely unavailable move.
Ready for Expert Sudoku?
Move to Expert when pairs and locked candidates feel natural and you can recover from a stalled grid by systematically rescanning candidates instead of guessing.
Try another Sudoku difficulty
Solve your own puzzleSudoku FAQ
What techniques are useful for Hard Sudoku?
Start with singles, then look for locked candidates, naked pairs, hidden pairs, and box-line interactions. Some grids may also expose an X-Wing.
Are fewer clues always harder?
No. Difficulty depends on the logical path required, not clue count alone. A puzzle with more givens can still require a more advanced elimination pattern.