How to play Expert Sudoku
- The Expert level is already selected; you can change it above at any time (Easy, Medium, Hard, Expert or Extreme).
- Fill the 9×9 grid so that every row, every column and every 3×3 box contains the numbers 1 to 9 without repeats.
- Turn on Notes and write the candidates of every cell from the start: at this level naked and hidden singles run out quickly and you have to look for patterns.
- If you get stuck, use Hint to fill in a cell (that game no longer counts for your best time) or Undo to go back.
What makes it “expert”
On this page the level does not depend on how many numbers are given at the start, but on the hardest technique needed to solve it. An Expert puzzle can always be solved by pure logic, but at some point it demands an advanced pattern: Y-Wing (a pivot with two wings that eliminate a common candidate), XYZ-Wing or Swordfish (the X-Wing extended to three rows or columns).
Before you get there you will need the Hard-level techniques: naked and hidden pairs and triples, box-line intersections, and X-Wing. If you have not mastered them yet, practice on Hard; if you want something even tougher, try the Extreme level, where you have to form a hypothesis and follow it through.
All the puzzles are generated on your device, with a verified unique solution, and rated by the same logic solver, so the level you see is the level the puzzle really has. Nothing is sent to any server.
Things to keep in mind
- Generating an expert puzzle can take one or two seconds on slow phones: it is built in the background and the page stays responsive.
- Your best time only counts if you do not use hints; the game and the records are saved only in this browser.
- The puzzles are rated using well-known techniques; someone who reasons differently may find them easier or harder than the level indicated.
Frequently asked questions
What techniques do I need for Expert Sudoku?
All those of the Hard level plus Y-Wing, XYZ-Wing or Swordfish. In the “Sudoku Solver” tool you can enter a puzzle and see step by step which technique each move needs.
Can it be solved without guessing?
Yes. An Expert puzzle can always be solved by logic; hypotheses with backtracking only appear at the Extreme level.
Do all the puzzles have only one solution?
Yes, this is checked when they are generated. A puzzle with more than one solution would not be a valid sudoku.
What is the difference from the Hard level?
Hard is solved with pairs, triples, intersections and X-Wing. Expert also needs short-chain patterns such as Y-Wing or Swordfish.
How long does an expert sudoku take?
Much longer than an easy one: it depends on how well you handle advanced techniques, and the first time it can take quite a while. There is no time limit.
Is it free? Do I need to install anything?
It is free, needs no sign-up and works right in the browser on a phone, tablet or computer.