What makes Hard Sudoku hard?
A Hard puzzle gives you 26 givens. That's the point where scanning for singles gets you started and then leaves you stranded - you'll fill a handful of cells, and then the easy moves simply stop. The grid won't budge until you bring a proper technique to it.
The good news: this is the level where guessing finally stops paying off, and that's a feature, not a bug. On Hard you learn to trust that a logical next step always exists, and to go looking for it methodically instead of stabbing at cells and hoping.
The techniques you'll actually need
Singles and pairs are still your workhorses, but Hard is where two more tools come into their own:
- Naked Pair - Two cells in a unit holding the same two candidates claim those digits, removing them elsewhere in the unit.
- X-Wing Sudoku Technique Explained - One digit confined to the same two columns across two rows (or vice versa) - eliminate it from the rest of those lines.
Alongside the naked pair, look for pointing pairs - when a candidate in a box is trapped on one line, it clears that number from the rest of the line. And this is the level where the X-Wing first shows up: your first genuine advanced pattern.
Moving up from Medium
Hard is the level where most players get stuck for a while, and it is worth knowing why: it is the first difficulty that cannot be finished with scanning alone. On Medium, careful scanning plus a few pencil marks always finds a way through. On Hard, there are positions where no cell is forced and no digit is obviously placeable - the only way forward is an elimination, removing a candidate rather than placing a number.
That is a genuine shift in how you play. Placing digits feels like progress; crossing out candidates does not, even though it is the move that actually breaks the grid. Players who stall on Hard are usually still hunting for the next placement, when they should be hunting for the next elimination.
Give yourself a few grids to make that switch. Once eliminations feel natural, Hard stops being a wall and starts being the level most people settle at - enough resistance to be interesting, not so much that it becomes work.
Solve it like a method, not a race
Hard grids reward a system. When you stall, don't stare at the same cell - change what you're looking at:
- Mark all your candidates. The advanced patterns are invisible until every possibility is on the board.
- Switch the digit you're chasing. A region that won't move for the 4s often cracks the moment you look at the 8s.
- Work the units, not the cells. Ask "where can this number go in this row?" rather than "what goes in this cell?"
Cleared a few of these? Expert Sudoku ups the ante again - fewer givens, and the advanced patterns become mandatory.
Prefer it on paper?
Every level here is also available as a printable sheet. The printable hard Sudoku page builds PDF pages at this exact difficulty - handy for a commute, a classroom, or anywhere a screen is in the way.
All five difficulty levels
Difficulty on SudokuStreak starts with how many digits the puzzle gives you, but the clue count is not the whole answer - and we can show that rather than assert it. On 31 August 2026 we generated 40 boards at every level and had our own solver finish each one, recording the hardest technique it was forced to use. The result was uncomfortable: 28 of the 40 Expert boards needed nothing harder than a hidden single, which is what Medium asks for. A 25-clue grid can still be a scan.
So Expert and Evil are no longer dealt straight from the generator. Boards for those two levels are measured first, away from the site, and only the ones that genuinely need the harder techniques are kept and handed out. That is what the last column below means: always is a floor the puzzle cannot fall below, usually is what the measurement found without one. The counts are for a standard 9×9 board:
| Level | Givens | Hardest technique needed (measured) |
|---|---|---|
| Easy Sudoku | 36 | usually naked single |
| Medium Sudoku | 30 | usually hidden single |
| Hard - you are here | 26 | usually hidden single |
| Expert Sudoku | 25 | always pointing or harder |
| Evil Sudoku | 23 | always box/line or harder |
The names are not standardised, though: "Expert" is the fourth rung of five here and the fourth of six elsewhere, and the hardest tier is called Evil on some sites and Extreme on others. Sudoku difficulty levels explained compares the common ladders and says what each level here actually asks of you.
Frequently asked questions
How many numbers does a Hard Sudoku puzzle start with?
Every SudokuStreak Hard puzzle on a standard 9×9 board is generated with 26 given digits, out of the 81 cells in the grid. Variants built on a different board set their own count for the same level - Samurai, for instance, is five overlapping 9×9 grids and fills each of them separately.
Do the puzzles always have exactly one solution?
Yes. However few givens a puzzle starts with, it has exactly one solution, and that solution is reachable by logic alone.
Do I ever have to guess?
No. Every puzzle can be finished by pure deduction. If you feel you have to guess, there is a technique on the board you have not spotted yet.
Is Hard Sudoku free to play?
Yes - every puzzle on SudokuStreak is free to play in your browser, with no account required. Signing in only adds streaks, scores and the leaderboard.
What techniques do I need for Hard Sudoku?
Naked and hidden pairs, and pointing pairs. At 26 givens, scanning for singles gets you started and then leaves you stranded - the grid will not budge until you work on candidates rather than on digits.
Can I print Hard Sudoku puzzles?
Yes. The printable hard Sudoku page generates PDF sheets at this exact difficulty, ready to print. You can start from the printable hard page.