Hard is the tier where scanning stops being enough. Each grid deals 28 to 32 numbers, leaving about 50 cells for you, and every grid is checked twice before you see it: once so it has exactly one solution, and once so that solution can be reached with pair logic alone. No guessing, and no need for anything deeper. Expect 15 to 30 minutes. Free in your browser, no download and no sign-up.
One thing, and it is worth being precise about it. On an Easy grid there is almost always a cell where only one digit can go. Find it, fill it, and that opens the next one. You can finish the whole puzzle that way without writing anything down.
A Hard grid runs out of those. Sooner or later every cell has two or more digits that would fit, and no amount of re-scanning changes that. The next move is not in any single cell — it is in the relationship between two of them.
That is the whole step up. It is also why the first thing to do on a Hard grid is turn notes on.
| Tier | Givens | Techniques it forces | Typical time |
|---|---|---|---|
| Beginner | 42–46 | Scanning, single candidate | 5–15 min |
| Easy | 36–40 | Scanning, single position | 5–10 min |
| Hard | 28–32 | Naked pairs, hidden pairs | 15–30 min |
| Evil | 24–27 | Pointing pairs, box-line reduction, triples | 30–60 min |
Every Hard puzzle here is graded against these before it is served. If you know all four, no Hard grid can stop you.
Two cells in the same row, column or box, each holding the same two candidates and nothing else. Those two digits have to go in those two cells, in some order. So they can leave every other cell in that unit. This is the most common opening on a Hard grid.
The same idea from the other direction. Two digits in a unit that can only go in the same two cells. Those cells belong to that pair, so every other candidate in them can go — even if each cell currently shows four or five options.
Look inside one box. If a digit can only sit in one row of that box, then it is in that row somewhere — so it cannot be anywhere else along the row, outside the box. Same for columns. This one reaches further across the grid than the pairs do.
The reverse of a pointing pair. If a digit within one row can only sit in cells that all fall inside the same box, then that digit belongs to that box, and it leaves every other cell in the box.
Our Sudoku tips and tricks page works through each of these with a worked example.
Clue count on its own is a poor description of difficulty. Blank 50 cells at random and you can get a grid that falls apart in four minutes, or one that cannot be finished by any known technique at all — the second kind has one answer, but the only route to it is guess and backtrack.
So each candidate grid goes through two checks. The first is uniqueness: a cell is only left blank if the puzzle still has exactly one solution without it. The second is a technique check. A solver walks the grid using the four methods above, cheapest first, and the puzzle is only served if that solver can finish it and if it actually had to use pair logic somewhere. A grid that singles alone would crack is not Hard, and gets re-rolled as an Easy candidate would.
That is what lets this page promise something specific: no Hard grid needs an X-wing, and none needs a guess.
One Hard grid a day, the same grid for every player, generated from the date. Your streak counts a day once, whichever tier you played, so a Hard day and an Easy day are worth the same to it.
Go to today's Daily Sudoku.
Same rules and the same board. What changes is how many numbers you start with and which techniques the grid forces.
Yes. Hard Sudoku on TrySolitaire is free, with no download and no sign-up. It runs in your browser, and can be installed as an app on any device, after which it works without an internet connection.
Between 28 and 32, so you fill in roughly 50 cells yourself. Easy deals 36 to 40 and Evil deals 24 to 27. The count varies from grid to grid, and the lower end of the band tends to be the longer solve.
Easy can be finished by scanning: for almost every empty cell there is a moment when only one digit fits, so you never need to write anything down. Hard cannot. Every Hard grid reaches a point where no single cell is decidable on its own, and you have to work with pairs of candidates instead. That is the step, and it is why notes mode stops being optional here.
Four, and no more. Naked pairs, hidden pairs, pointing pairs and box-line reduction. Every Hard grid we deal is checked to be solvable with those, so you never need an X-wing and never need to guess. If you find yourself reaching for something deeper, there is a simpler step you have missed.
Usually 15 to 30 minutes. Easy grids take 5 to 10 and Evil grids 30 to 60. Most of the extra time on Hard goes into filling in and maintaining pencil marks rather than into the deductions themselves.
Yes, and it is checked rather than assumed. A cell is only left blank if the grid still has a single solution with it gone. That matters because the board grades what you type against the solution, so a puzzle with two valid answers could mark a correct entry wrong.
In practice, yes. Pairs are the whole tier, and you cannot see a pair without seeing the candidates. Turn notes on and mark every digit that could go in each empty cell. The patterns appear on their own once the marks are there.
Yes. The print option produces a sheet of grids at the difficulty you choose, with the solutions on a separate page. Printed puzzles come from the same generator, so they carry the same single-solution guarantee.
28 to 32 givens, one checked solution, and four techniques that always get you there. Free in your browser.
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