Printable hard sudoku with room for notes

Printable hard sudoku sheets with 26 to 30 clues per grid, each needing naked or hidden pairs, triples or box-line reduction. Print 1 to 12 puzzles, one to six per page, with answers at the end. The PDF is made in your browser: no app, no sign-up, no interstitial, works offline and with the keyboard.

How to print hard sudoku sheets

1. Hard is selected; choose 1 to 12 puzzles.
2. Pick two or four per page. Hard grids are much easier with pencil marks, which need space.
3. Choose A4 or Letter and normal or large print.
4. Include solutions to get answer pages at the end.
5. Create the PDF and print it. The sheet code recreates it later.

Printable hard sudoku: what the grids need

Every Hard grid needs at least one naked pair or triple, hidden pair or triple, or box-line reduction, on top of singles and pointing pairs. These remove candidates rather than place digits, so on paper you need notes.

Write candidates small in the corners of each cell, or in a fixed position (1 top left, 9 bottom right) so pairs stand out. Use a pencil with an eraser. A naked pair is two cells in a unit with the same two candidates; cross those digits out of the unit’s other cells. A hidden pair is two digits that appear in only two cells of a unit; erase everything else from those cells.

The daily sudoku online is also Hard by default, so a Hard sheet is good practice for it. In a club or classroom, one sheet code for everyone makes comparing times fair.

For travel, two per page gives generous room and six grids fill three sheets.

Box-line reduction, the last Hard technique, is the mirror of a pointing pair: when a digit’s candidates in a row or column all lie inside one box, it can be erased from the rest of that box. It is easy to miss on paper, so check for it whenever a row or column has only two or three candidates for a digit.

What a hard sudoku PDF contains

Pages are titled "Hard Sudoku" with the sheet code and show a rule line, numbered puzzles and page numbers. Solutions follow on separate pages, givens in bold. The PDF is built on your device.

Plays anywhere, no app, no account

Hard sudoku sheets can be made on a phone and printed from any PDF viewer. Tidy Puzzles runs entirely in your browser: there is no app to install, no account to create and no interstitial before you can play. After the first visit the game also works offline, because each puzzle is generated on your device from a seed. Every board can be played with the keyboard alone, on a phone or a desktop, and your stats and unfinished puzzles stay in this browser rather than on a server.