What makes Expert so tough?
Expert X-Sudoku gives you the smallest number of starter clues we use anywhere on the site. The diagonals are essentially the whole solving engine for the first half of the puzzle. You’ll need to hold a lot of information in your head (or in Notes) at once.
But every Expert puzzle on this site has exactly one answer, and you can solve it without guessing. Use logic, take breaks, trust your notes!
If Expert feels overwhelming, that’s normal — even adults find it tough. Spend a few weeks at Hard X-Sudoku first; the techniques are exactly the same, just with one or two more starter numbers.
Techniques worth memorising
- 🔢 Hidden singles on both diagonals — scan every time you place a new digit
- 🔢 Naked pairs and naked triples on rows, columns, boxes and diagonals
- 🔢 Pointing pairs: if a digit in a box can only go in two cells on a diagonal, that digit is locked on the diagonal
- 🔢 X-Wing: in classic sudoku it’s uncommon, but in X-Sudoku the two diagonals make X-Wings much easier to spot
Expert solving routine
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Auto Notes first
Tap it the moment the puzzle loads. You’ll see every candidate digit at a glance.
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Work the centre cell
It sits on both diagonals. Any progress here ripples to lots of other cells.
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Scan both diagonals every move
After every single placement, glance at both diagonals. Hidden singles appear all the time.
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Hunt naked pairs and triples
After Auto Notes, look for two cells with the exact same two candidates on any row, column or diagonal — those numbers are locked there.
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Place, repeat, win
Each placement narrows things down everywhere. Keep going until the board is full!
When you’ve mastered Expert
Once Expert X-Sudoku feels comfortable, try our toughest Expert 9×9 sudoku. It’s a different kind of challenge — no diagonals, pure row/column/box logic — but the same long-thinking patience pays off.
Or try Killer Sudoku for puzzles that replace the diagonals with cage sums, or Jigsaw Sudoku for puzzles with wiggly regions instead of 3×3 boxes. Very different puzzles, all built on the same "one of each in every line" idea.
Frequently asked questions
How long does an Expert X-Sudoku take?
Most kids who can solve Expert finish in 20 to 40 minutes. Some take more than an hour — that’s normal! There’s no time limit.
Can I really solve Expert without guessing?
Yes! Every puzzle on this site has exactly one solution and was checked by computer to be solvable with logic alone. If your guess turns out wrong, just tap Undo.
What if I’m really stuck?
Tap the Hint button — it fills one correct cell so you can keep going. Hints count in your stats, but they’re there to help.
Is there anything harder than Expert X-Sudoku?
On this site, Expert is the toughest diagonal puzzle. Some grown-up sites have an "Extreme" or "Diabolical" level, but those are designed for adult sudoku-club regulars, not kids.
Try other sudoku games
Different rules, same friendly board. Pick a sibling puzzle to play next.