Hard Sudoku to Print
Print hard 9x9 sudoku with answer pages, or play one on screen with technique hints.
How to print hard sudoku
The Print tab opens first. Work through these steps:
- Set the number of puzzles per page and the number of pages (1 to 20).
- Choose paper size: US Letter or A4.
- Leave ‘Add answer pages at the end’ on if you want answers. Answer grids are smaller, several to a page, and numbered to match the puzzles.
- Turn on ‘Show title and difficulty above each puzzle’ if you want each puzzle labelled, for example “Sudoku — Hard — #3”.
- Check the preview of page 1 and its answer page.
- Click ‘Print / Save as PDF’. In the browser print dialog, choose ‘Save as PDF’ as the destination to get a PDF file.
Puzzles are made one at a time, and a progress counter shows “Making puzzle 3 / 12…”. Press Cancel to stop.
The footer of each page shows the set’s seed. Enter that seed in the Seed field under ‘Repeat or share this set’ with the same settings, and you get the same puzzles again. On the Play tab, click a cell, then a number on the number pad or type a digit. Pencil mode (the P or Space key) writes small candidate notes instead of a digit. Arrow keys move, Backspace erases, and Ctrl/Cmd+Z undoes. Your progress is saved on this device, and Copy link opens the same puzzle on another device.
How to solve a hard sudoku
A hard sudoku needs at least one advanced technique: a naked or hidden triple, an X-Wing, a Y-Wing, a Swordfish or an XYZ-Wing. Every hard puzzle here can be finished without guessing. The rules are the classic ones. Each row, column and 3x3 box must contain the digits 1 to 9 exactly once, and the given digits cannot change.
Difficulty depends on the techniques needed, not on the number of clues. In the site’s generator, hard 9x9 puzzles had 26 to 30 clues, almost the same as medium puzzles (26 to 29). A puzzle with few clues is not automatically harder.
A practical order:
Fill every single first, both naked and hidden. Write all candidates in pencil in the empty cells. Look for locked candidates: when a digit’s possible cells in one box all sit in a single row or column, remove that digit from the rest of that row or column. Then check naked and hidden pairs and triples. Move to fish and wings only when those stall.
X-Wing: if a digit can go in only two cells in each of two rows, and those four cells sit in the same two columns, remove that digit from the other cells in those columns.
Y-Wing: a pivot cell holds candidates X and Y. Two wing cells hold X with Z and Y with Z, and each wing sees the pivot. Z can be removed from any cell that sees both wings.
How to solve hard sudoku without guessing
You can, on these puzzles, because each one has a logical path using the techniques above. Guessing is never needed. The most common reason for getting stuck is a wrong pencil note, so keep notes tidy. Turn on ‘Remove pencil marks automatically’ so that placing a digit clears that digit from the cells it sees. Use Check to find wrong cells in red, and undo if a placement looks wrong.
How to solve expert and extremely hard sudoku
Some puzzles cannot be finished with the twelve techniques this site teaches; the solver rates those “expert”. They still have exactly one solution, but they need longer chains of reasoning or trial and error: pick a cell with two candidates, follow one choice until it leads to a contradiction, and the other choice is then proven. The puzzles on this page are rated hard, so they never need that. To test an expert grid from a book, type it into the sudoku solver: Next step shows how far logic gets before guessing would be needed.
Frequently asked questions
Can I print hard sudoku with answers?
Yes. Leave ‘Add answer pages at the end’ on, and the answer grids are added after the puzzles. They are smaller, several to a page, and numbered to match the puzzles.
How do I save hard sudoku as a PDF?
Click ‘Print / Save as PDF’, then choose ‘Save as PDF’ as the destination in the browser print dialog. Check the preview of page 1 first.
How can I print the same hard sudoku set again later?
Note the seed shown in the page footer. Enter it in the Seed field under ‘Repeat or share this set’, using the same settings, and the same puzzles are made again.
How to solve hard sudoku when stuck?
On the Play tab, press Hint. It names the technique for the next step, such as Hidden Single or Naked Pair, highlights the cells and explains it in one sentence. If one of your digits is wrong, it asks you to fix that first.
Does every hard sudoku here have one solution?
Yes, and it can be reached by logic alone, without guessing. Every puzzle is checked by the built-in solver to have exactly one solution before it is shown.
Related tools
- Easy sudoku: use it for a gentler start, since its puzzles need only singles.
- Medium sudoku: use it when you want a step up before hard puzzles.
- Printable sudoku: use it to print a mix of puzzle sets.
- Daily sudoku: use it when you want the daily puzzle.
- How to play sudoku: use it if you need the basic rules first.
- Sudoku solver: use it to look up the solution to a grid you are working on.
- 4x4 sudoku: use it for a smaller grid with fewer digits.