What makes Expert so tough?
Expert gives you no starting numbers at all. Not one. That sounds impossible, but it is exactly how Kropki is set in puzzle championships: fill a sudoku, mark every line honestly, rub out all eighty-one digits, and what is left almost always still has exactly one answer. We only use the boards where it does.
With nothing filled in, there is nothing to read a line against — so the first moves come from the dot shapes and the chains. Black dots throw out 5, 7 and 9; white dots throw out 1; a square with black dots on both sides is a 2 or a 4; a run of three black dots is 1-2-4 or 2-4-8. Once the first digit lands, the empty lines around it wake up, and the puzzle starts to behave like a very hard Hard.
If Expert feels overwhelming, that is normal — plenty of adults find it tough. Spend a few weeks at Hard Kropki Sudoku first; the techniques are exactly the same, just with eight starting numbers to lean on.
Techniques worth memorising
- 🚫 The shape sweep — cross 5, 7 and 9 out of every black-dotted square and 1 out of every white-dotted square before you do anything else
- ⚫ Black-dot runs are always 1-2-4-8 or 3-6, so three black dots in a row have just two readings
- 🪜 The staircase on every run of white dots — the middle of three is never 1 or 9
- 🕳️ The empty-line read, every single time you place a digit
- 🔢 Naked pairs and naked triples in rows, columns and boxes
- 🎯 Hidden singles: a digit that can only fit in one square of a row, column or box
Expert solving routine
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Auto Notes first
Tap it the moment the puzzle loads. With no numbers to read against it will only apply the dot shapes — but that alone empties 5, 7 and 9 out of every black-dotted square, which is a real start.
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Squeeze every chain
Walk each run of dots end to end and erase any candidate that no longer has a partner next door. Black-dot runs first: they are the shortest and the strictest.
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Place from the ends
The two ends of a chain often have just one possible value left. Solve those first and the middle usually falls right after.
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Wake up the empty lines
Every digit you place turns its empty neighbours into clues. Re-read all four lines around each new digit before you look anywhere else.
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Place, repeat, win
Every placement narrows things down everywhere else. Keep going until the board is full!
When you have mastered Expert
Once Expert Kropki Sudoku feels comfortable, try our toughest Expert 9×9 sudoku. It is a different kind of challenge — no dots, pure row, column and box logic — but the same long-thinking patience pays off.
Or take on Greater Than Sudoku, where > and < signs replace the dots, Thermo Sudoku, where whole thermometers do the job, Hyper Sudoku for four extra mini-boxes, Killer Sudoku for cage sums, or Jigsaw Sudoku for wiggly regions instead of 3×3 boxes. Very different puzzles, all built on the same "one of each in every region" idea.
Frequently asked questions
How long does an Expert Kropki Sudoku take?
Most kids who can solve Expert finish in 25 to 45 minutes. Some take more than an hour — that is completely normal, and there is no time limit.
Can I really solve a board with no numbers on it?
Yes! Every Expert puzzle on this site has exactly one solution and was proved by computer before it appeared. The dots and the empty lines carry all the information you need. If a guess turns out wrong, just tap Undo.
What if I am really stuck?
Tap the Hint button — it fills in one correct square so you can keep going. On an empty board even one digit makes a huge difference, because the empty lines around it become clues. Hints count in your stats, but they are there to help.
Is there anything harder than Expert Kropki Sudoku?
On this site, Expert is the toughest dot puzzle, and a zero-given Kropki is the published form of a hard Kropki everywhere. Some grown-up sites offer "Extreme" or "Diabolical" levels of other variants, but those are designed for adult puzzle-club regulars rather than kids.
Try other sudoku games
Different rules, same friendly board. Pick a sibling puzzle to play next.