Advanced Sudoku techniques

Advanced Sudoku techniques for harder boards

When basic singles and pairs stop moving the grid, these intermediate patterns give you the next set of reliable eliminations.

This page covers subsets from pairs to quads, X-Wing through Swordfish, wing patterns, and single-digit patterns like Skyscraper and Two-String Kite.

What this page is for

Start with subsets and work into fish and wings. Every slide shows the shape, the cleanup move, and the logic that makes it trustworthy.

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  • Move from note cleanup into genuine pattern spotting.
  • Study one advanced technique at a time instead of memorizing names without context.
  • Use hardcoded boards to see exactly where candidates survive and where they disappear.
  • Carry the same logic back into hard and very hard puzzles on the live board.

Advanced walkthroughs

Start with subsets and work into fish and wings. Every slide shows the shape, the cleanup move, and the logic that makes it trustworthy.

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Only two cells in the highlighted box can still hold 4 or 8.

Advanced entry point

Hidden Pair

Two digits only fit in the same two cells inside one unit. Once you spot them, every other candidate in those cells can go.

How to read it

  1. 1Scan one row, column, or box for digits that appear in exactly two candidate cells.
  2. 2Check whether those two digits share the same two cells.
  3. 3Strip every other note from those cells and rescan the connected units.

What it unlocks

Hidden pairs turn messy note clusters into cleaner structures. They often sit between beginner logic and heavier pattern work.

Ignore how crowded the cells look. If only two spots in the unit can hold 4 and 8, those spots belong to the pair even before the rest of the notes are cleaned up.

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Advanced technique questions

When should I start studying advanced techniques?

Start when singles, notes, pairs, and locked candidates stop creating steady progress on hard boards. That is usually the point where pattern recognition becomes worth the effort.

What is the most useful advanced technique?

X-Wing and XY-Wing give the best return on investment. They appear frequently and the pattern is small enough to spot reliably once you have practiced.