Sudoku puzzles
Hard Sudoku Puzzles
Puzzles that cannot be finished with the basic moves alone: each needs at least one more advanced deduction.
Free printable PDF
Download this sheet and its answer key as shown, and print it at home or school. No account needed.
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- Grid
- 9×9
- Difficulty
- Hard
- Puzzles per page
- 2
- Solutions
- Included
- Paper
- US Letter or A4
About this worksheet
Every hard puzzle here reaches a point where neither basic move finds the next digit. To get past it you will need a technique such as locked candidates (a digit confined to one row inside a box) or a naked pair (two cells in a unit that share the same two candidates).
Pencil marks are close to essential at this level. Fill in the candidates for each empty cell, then look for pairs and for digits that are confined to one line within a box.
- 01
One solution, every time
Each puzzle is checked to have exactly one solution, so it can always be finished by reasoning, never by guessing.
- 02
Solutions included
The sheet ends with a solutions page, with the filled-in digits in red so they stand out from the clues.
- 03
New puzzles in one click
Open the sheet in the editor to deal a fresh set at the same size and difficulty whenever you need another page.
More sudoku puzzles
Questions
- How is the difficulty decided?
- By the solving techniques a puzzle needs, not just by how many clues it has. Easy and medium puzzles can be finished by finding the one digit that fits a cell or the one cell where a digit fits; easy puzzles also keep extra clues. Hard puzzles need at least one step beyond that, such as spotting a pair of cells that share the same two candidates.
- Which techniques do hard puzzles need?
- At least one of locked candidates, naked or hidden pairs, naked triples, or an X-wing, along with the basic moves. None of them need trial and error.
- Are these hard sudoku puzzles free?
- Yes. The sample sheet on this page, with its solutions, is a free PDF in US Letter or A4, no account needed. Dealing and previewing new puzzles is free too; printing and downloading custom sheets come with Pro, which also removes the preview watermark.