Classic Sudoku

Extreme Sudoku

Play free Extreme Sudoku online. Every Extreme puzzle here needs at least one advanced pattern, such as a Skyscraper, an XY-Wing or an X-Wing, found by logic, never by guessing.

10,000+ puzzles21 to 32 cluesOne solution each
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An Extreme puzzle from our collection, 26 clues

What makes a Sudoku Extreme here

Every puzzle on Sudoku Challenge is solved by our grader step by step, the way a careful person would: at each step it uses the simplest technique that works. A puzzle's level is the hardest group of techniques it cannot be finished without.

Easynaked singles only: every step is a cell with one possible digit.
Mediumadds hidden singles (a digit with one possible cell in a row, column or box) and locked candidates.
Hardadds pairs, triples and quads, naked and hidden, the unique rectangle and BUG+1.
Extremeneeds at least one advanced pattern, such as the X-Wing, XY-Wing, Skyscraper or Swordfish.
Diabolicalneeds the longest chains and largest patterns our solver knows, such as the XY-Chain, Jellyfish or ALS-XZ.

So an Extreme puzzle is one that every Hard technique together cannot finish, yet never needs the longest chains of Diabolical or a guess. Its score sits between 5,000 and 7,999 points, shown before you start.

Our Extreme puzzles have 21 to 32 clues, 25 on average, about as many as our Hard ones. What counts is the techniques.

The techniques you need

First the ones from the easier levels that Extreme puzzles use most: Naked Single, Hidden Single, Locked Candidates, Naked Pair, Hidden Pair and Unique Rectangle. Then the Extreme techniques, with how often our grader used each one across our 10,000+ Extreme puzzles:

TechniqueExtreme puzzles using it
Naked SingleEasy levelevery one
Hidden SingleMedium levelevery one
Locked CandidatesMedium level89%
Naked PairHard level43%
Hidden PairHard level33%
Unique RectangleHard level28%
X-Wing15%
Skyscraper50%
Two-String Kite20%
Empty Rectangle10%
XY-Wing38%
W-Wing19%
Simple Coloringunder 1%
Swordfishunder 1%

Counted October 2026 over every puzzle on the site. More in Sudoku by the Numbers.

How to solve an Extreme Sudoku

  1. Fill in every candidate, and clear what the easier techniques can: singles, locked candidates, pairs and triples.
  2. When they stop, take one digit at a time. Two rows where it has exactly two places, lined up at one end, make a Skyscraper: any cell that sees both other ends cannot hold that digit.
  3. Two rows where the digit has two places each, in the same two columns, make an X-Wing: eliminate it from the rest of those columns.
  4. Then the cells with two candidates: a pivot and two wings that each share one of its digits make an XY-Wing.
  5. After every elimination, go back to the singles: one advanced move usually opens several easy ones.

Extreme puzzles across the site

Play ExtremeAn unlimited supply in Classic, with candidates, Next Step hints and undo.The Daily TripleThree Extreme or Diabolical puzzles a day, the same for everyone, with a leaderboard.Printable Extreme SudokuPacks of 12 to print, with the answers on the last page.Learn the techniquesEvery technique above, step by step, with real examples.
The other levels:Easy SudokuMedium SudokuHard SudokuDiabolical Sudoku

Questions about Extreme Sudoku

What is the difference between Hard and Extreme Sudoku?

A Hard puzzle falls to pairs, triples and the unique rectangle. An Extreme puzzle needs at least one more advanced pattern: across our Extreme puzzles the Skyscraper is used in about half, the XY-Wing in more than a third and the X-Wing in about one in seven.

Is Extreme the same as expert Sudoku?

Many sites call this level Expert. Here it is called Extreme, the step between Hard and Diabolical.

Do Extreme puzzles need guessing?

No. Every Extreme puzzle here can be solved by logic with the techniques on this page, and has exactly one solution.

Where can I play Extreme Sudoku against others?

In the Daily Triple: every day each of its three puzzles is Extreme or Diabolical, the same for everyone, with a leaderboard. Tournaments and duels are played at Easy, Medium and Hard.