Master Sudoku Puzzles (Evil Level)
Master Sudoku, the level many sites call Evil, starts with 23 to 28 givens, sometimes barely a quarter of the grid. Placing digits by scanning alone gets you only a few moves in. From there, Master boards demand real candidate work: naked pairs that lock two digits into two cells, pointing pairs that pin a digit to one line inside a box, and hidden singles that only appear once those eliminations have been made. Every puzzle still has exactly one logical solution, but finding it takes method.
How Master boards are built
The generator removes givens until the board is as sparse as it can be while keeping a unique solution, then checks which techniques a solver needs. Puzzles that fall to singles alone are thrown out. What remains is a board where at some point the only way forward is an elimination: proving that a candidate cannot be somewhere, rather than proving where a digit must go.
Master Sudoku techniques and candidate management
At this level notes are not optional. A reliable routine looks like this:
- Fill candidates for every empty cell before you look for moves. Be complete; a missing candidate produces a wrong "single" later.
- After each placement, remove that digit from the notes of its row, column and box. The game does this for you automatically; keep it switched on.
- Scan each unit for two cells that share exactly the same two candidates. When you find a pair, strip those digits from the unit's other cells.
- Scan each box for a digit whose candidates all lie on one row or column, and clear the digit from the rest of that line.
- Only now look for naked and hidden singles again. Eliminations create them.
Evil Sudoku tips: staying accurate
Master puzzles are lost to sloppy notes far more often than to hard logic. If the board seems contradictory, a candidate was erased that should not have been, or one was never written. Undo is unlimited; use it generously. And remember that the three hints are worth most when you are genuinely stuck, because a single revealed digit can collapse a whole region of candidates.
Beyond Master
Extreme Sudoku reduces the givens to 22 or 23 and brings in patterns such as X-Wing and XY-Wing. If Master is a step too far right now, Expert Sudoku uses the same ideas on a friendlier board.
Frequently asked questions
Is Master Sudoku the same as Evil Sudoku?
Yes. Evil is the name several sites use for the level between Expert and Extreme. Our Master level covers the same band: 23 to 28 givens and puzzles that require naked pairs and locked candidates.
How many givens does a Master Sudoku have?
Between 23 and 28. Boards are stripped down as far as the unique-solution requirement allows, then checked for the techniques they need.
Which techniques do Master puzzles require?
Hidden singles, naked pairs, and locked candidates (pointing pairs and box/line reduction). Around four boards in ten need the pair and locked-candidate eliminations; the rest are long chains of hidden singles.
Is Master the hardest level?
No. Extreme is one step further, with fewer givens and advanced patterns such as X-Wing.