🔢 This free printable sudoku prints on a single page. The answer key sits in a small strip at the bottom — fold it backward along the dotted line before you start, and you can solve honestly without ever seeing the solution. A real challenge — high-school level reasoning and vocabulary recommended.
Fill the grid so every row, every column, and every 3×3 box contains the digits 1 through 9 exactly once. Fewer starting clues — sharper logic required.
8
6
9
3
3
9
7
2
3
8
4
8
2
3
2
6
9
7
3
8
1
7
1
6
4
7
9
2
1
7
9
7
8
6
1
✂ fold backward along this line to hide the solution ✂
Solution hidden on screen — it prints automatically.
Solution
8
4
5
6
9
2
1
3
7
1
3
9
4
5
7
6
2
8
2
6
7
3
1
8
4
5
9
4
8
1
2
6
5
9
7
3
5
2
6
9
7
3
8
1
4
7
9
3
8
4
1
2
6
5
6
1
4
7
3
9
5
8
2
3
5
8
1
2
4
7
9
6
9
7
2
5
8
6
3
4
1
How to Solve This Sudoku
A Hard-rated grid usually has a handful of cells that resist simple scanning until you bring in a sharper technique. Here's where to focus:
Hunt hidden singles inside boxes. Even when a cell looks like it has several candidates, check whether one of those candidates is the only place a given number can go anywhere in that box — that locks it in.
Chain your eliminations. Removing one candidate from one cell often triggers a domino effect that clears candidates elsewhere. Re-check the whole grid after each confirmed number rather than only the immediate neighbors.
Isolate one box at a time. When you're stuck, pick the box with the fewest empty cells and work it in isolation against its row and column constraints before moving to the next.
These intermediate moves are usually enough to crack a Hard grid without guessing. For pairs, triples, and more advanced patterns, see our complete Sudoku strategy guide.
About This Puzzle
Hard Sudoku #4 doesn't give you a single 5 anywhere on the starting grid — every one of the nine 5s has to be placed entirely through deduction, with no starting point to work from. It's a genuinely different kind of challenge from the other three hard puzzles, which each start with at least one of every digit.