Generator · Print-true
Printable sudoku
Fresh sudoku puzzles, generated on your device rather than pulled from a puzzle bank, with the single-solution property proved for every grid before it prints. Four difficulty levels, one to four puzzles a page, answer keys included — no watermark, no account, nothing uploaded.
How this generator works
A sudoku is built here in two stages, and the first one is not a search at all. A complete, valid solution grid is produced by taking one known-good pattern and applying only transformations that cannot break it: relabelling the nine digits, shuffling the three rows inside each band, shuffling the bands themselves, doing the same to columns and stacks, and sometimes transposing the whole thing. Every one of those moves preserves the row, column, and box constraints, so the finished grid is correct by construction rather than by verification — and there are enough distinct combinations that two visitors pressing "New puzzles" will not meet.
The second stage removes clues, and this is where the single-solution promise is actually earned. Cells are cleared two at a time in 180-degree-rotational pairs, which is what gives a printed sudoku its familiar symmetry, and after every removal a backtracking solver counts how many ways the grid can now be completed, stopping the moment it finds a second. Only removals that leave exactly one solution are kept; anything else is put straight back. Digging continues until the target clue count for the chosen difficulty is reached or no further symmetric pair can leave without making the puzzle ambiguous — and because the real count is printed above each grid, you can see which happened.
The honest limits. Difficulty here is clue count, which is a proxy rather than a technique rating: a 27-clue grid that falls to plain scanning is genuinely easier than a 30-clue grid that needs an X-wing, and this page does not claim to grade solving paths. Symmetric digging is also an aesthetic choice that costs clues. The proven minimum for a sudoku of any shape is 17 givens, but the grids that reach it are deliberately asymmetric; insisting on rotational symmetry throws away most of that search space, and the symmetric grids here bottom out in the low twenties. Expert targets 24 for that reason. Grids that go below it do occur and print their real count, and grids that stop a clue or two above it occur too — which is why the count above each puzzle is the one to trust, not the label. Twelve expert puzzles take a moment to generate, because each is proved unique the hard way and the clue-removal pass is retried up to twelve times to get as deep as the target asks. And as with every sheet here, print at 100% or "Actual size"; "Fit to page" rescales the grid.