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Sudoku, taught properly

22 solving techniques, from the first easy single to the Jellyfish — each one explained, diagrammed, and practised.

Solving techniques are the patterns behind every Sudoku ever solved without guessing. Each one is a small piece of logic — a way of reading a row, a box, or a set of pencil marks that either places a digit or proves one impossible somewhere. Learn them in order and puzzles stop being trial and error: hard boards become a sequence of moves you know how to find.

Every technique below gets a full walkthrough on this site, drawn on a real board. And each has an interactive step-by-step demo in the Puzzlesight app — the very same boards you see here — plus generated practice puzzles that can only be cracked with the technique you are learning. Read it here, then make the move yourself.

The Swordfish tutorial in the Puzzlesight app — an interactive board stepping through the technique
The in-app tutorial — every step on a live board
Start here The rules of Sudoku New to the puzzle? The grid, rows, columns, and boxes — plus givens, entries, and notes — in six short steps, before the first technique.

Easy

  1. 01 Full House One empty cell left in a house — the last digit writes itself.
  2. 02 Naked Single A cell whose pencil marks have dwindled to a single digit.
  3. 03 Hidden Single The cell still has options — but the house has only one place for the digit.

Medium

  1. 04 Pointing Pair A box pins a digit to one line — and the line outside the box pays for it.
  2. 05 Box/Line Reduction A row claims a digit inside one box — the rest of the box lets it go.
  3. 06 Naked Pair Two cells, the same two candidates — no one else may have them.
  4. 07 Hidden Pair Two digits with only two homes — everything else in those cells is noise.

Hard

  1. 08 Naked Triple Three cells sharing three candidates lock each other in.
  2. 09 Hidden Triple Three digits confined to three cells — buried under other pencil marks.
  3. 10 X-Wing Four corners of a rectangle trap a digit across two rows at once.

Extreme

The deep end: quads, the bigger fish, single-digit link patterns, the wings, and the uniqueness arguments. Take them in ladder order — each one leans on the moves before it.

  1. 11 Naked Quad Four cells, four shared candidates — the rest of the house goes without.
  2. 12 Hidden Quad Four digits squeezed into four cells — everything else there is noise.
  3. 13 Swordfish The X-Wing grown by a line: three rows cage a digit in three columns.
  4. 14 Skyscraper Two towers for one digit share a base — cells seeing both roofs lose it.
  5. 15 Two-String Kite A row string and a column string meet in a box — and cut a cell far away.
  6. 16 XY-Wing A pivot and two pincers: whichever way it tips, the same digit falls.
  7. 17 XYZ-Wing An XY-Wing whose pivot holds the shared digit too — tighter, but just as sharp.
  8. 18 W-Wing Twin pairs joined by one strong link — the other digit cannot escape both.
  9. 19 Empty Rectangle A box hugs one row and one column — its empty corner powers a distant strike.
  10. 20 Unique Rectangle Four corners that would allow two solutions — so one of them cannot happen.
  11. 21 BUG+1 Every cell down to two candidates but one — the odd cell out must resolve.
  12. 22 Jellyfish Four columns pin a digit to four rows — the fish family, fully grown.
Learn by doing

Every technique, hands-on in the app

The app walks each technique step by step on an interactive board, then generates practice puzzles that require the move you just learned.

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The Naked Pair tutorial in the Puzzlesight app, mid-walkthrough with the pair highlighted in column 7
Step-by-step, on a board you can touch