Hard Sudoku Hard puzzles, free to print
Hard sudoku that needs techniques such as pairs. Free to print, with answers, and 30 stages are free in the browser with no sign-up.
Who it's for Anyone who wants more than Medium, likes learning techniques, and is happy to spend 30 minutes to 1 hour on a puzzle.
- Typical time30 min to 1 hr
- CluesAverage of 27
- Printable puzzles500 puzzles
- Free to play30 stages
今日の上級の問題を解く →上級の印刷用 500 問（答えつき）
- Print All 500 free, with answers
- Browser 30 stages free
- Other puzzles A ticket per puzzle (none needed with the Lounge Pass)
Today's Hard puzzle11/13
Changes every day at 0:00 Japan time.
1The way into Hard is the Naked Pair
In Hard, even with notes you stop finding cells with only one candidate. That is when you need techniques that use combinations of candidates to remove candidates from other cells.
In the row above, the 2 cells on the left both have only 3 and 7 as candidates. 3 and 7 are used up by these 2 cells, so 3 and 7 go from the other empty cell of the same row, and it must be 1.
Tips for Hard
- Pairs are easiest to find by starting with cells that have only 2 candidates. See whether the same row, column or box has another cell with the same 2.
- Conversely, if 2 digits can go only in the same 2 cells, that is a Hidden Pair. The other candidates in those 2 cells can be removed.
- In Hard, notes you forgot to erase are a common reason for getting stuck. If you cannot go on, check that no notes remain for digits already placed.
Techniques for Hard
Guides with examples
2How the levels differ
Levels are set not by how many digits are given at the start, but by the reasoning a puzzle needs.
| Levels and key techniques | Typical time | Clues |
|---|---|---|
| EasyJust find the missing digits | 5 to 20 min | 38 |
| MediumWrite notes (candidates) and narrow down | 15 to 30 min | 30 |
| HardRemove candidates with pairs | 30 min to 1 hr | 27 |
| OniPatterns that span the board, such as the X-Wing | 1 hr or more | 28 |
Hard and Oni start with about the same number of clues (averages of 27.2 and 27.6). Even with many digits, you cannot get far in Oni without finding patterns that span the board, such as the X-Wing.
The game has one more level above Oni, called Master, making 5 levels in all. Master can only be played in the game.
3Hard stages, chapter 1
These are the first 10 puzzles of the game's Hard stages. Chapter 1 is open from the start and free to play. Press a board to open that stage in your browser; the stars you earn stay on the stage.
- 963421984875233675792135869Stage 1-127 cluesSolve →
- 3643856736574541987261694957Stage 1-228 cluesSolve →
- 176578426192349756149526187Stage 1-327 cluesSolve →
- 57283459736192584173634879Stage 1-426 cluesSolve →
- 425714592781512328549429257139Stage 1-530 cluesSolve →
- 421938236782975187458496Stage 1-624 cluesSolve →
- 5237839496748862593785646475Stage 1-728 cluesSolve →
- 75284137156954321269746891Stage 1-826 cluesSolve →
- 294898537185624173734921146Stage 1-927 cluesSolve →
- 83952163864891731864793822341Stage 1-1029 cluesSolve →
4How to play
- Open a puzzle Press "Solve today's Hard puzzle" and the board opens in your browser. No app or sign-up needed. In the browser, Hard takes a ticket per puzzle (none needed with the Lounge Pass).
- Enter digits Select a cell and press a digit below. With "Notes" you can write small candidates.
- Stuck? Use a hint It does not show the answer straight away. It guides you in steps, starting with where to look.
For the rules and how to solve, with diagrams, see how to solve sudoku, with tips.
5Questions
What techniques does Hard use?
After carefully writing out your notes (candidates), you remove candidates using Naked Pairs, Hidden Pairs and the like.
Can I play Hard puzzles for free?
In the browser, these are free: the 10 puzzles of stage chapter 1 on this page, everything up to chapter 3 (30 puzzles), and the Daily puzzle, whose level changes by day of the week. Chapters from 2 on open when you clear 7 puzzles of the chapter before. Other Hard puzzles take a ticket per puzzle, and the Lounge Pass lets you play as many as you like. All 500 printable puzzles are free and come with answers.
Do I need to guess (trial and error)?
No. Every puzzle has been checked to be solvable by logic alone, without trial and error or proof by contradiction.
How do Hard and Oni differ?
In Hard, you remove candidates using combinations within one column, row or box. In Oni, you need to find patterns such as the X-Wing, which remove candidates across 2 separate rows or columns.
What if I get stuck?
Hints guide you in order: the place to look, the name of the technique, then that technique's guide page.