All Sudoku Variants
9×9 · Constraint

Clone Sudoku

Two or more shaded regions are clones — identical in shape and filled with the same digits in the same arrangement.

3 8 3 8 1 9

An example Clone puzzle: the two shaded clones hold the same digits in the same arrangement — 3, 8 copied cell for cell.

Clone Sudoku shades two or more regions that are clones of each other: identical in shape, and filled with the same digits in the same arrangement. Whatever goes in one clone must be copied, cell for cell, into every other clone — a mirror that links distant parts of the grid together.

The rule: clones hold matching digits

Cloned regions share their shape wherever they sit, and corresponding cells hold the same value. Below, two three-cell clones both read 4, 7, 2 — the second is an exact copy of the first.

4 7 2 4 7 2

Two clones, both 4-7-2: corresponding cells always match.

A worked example, step by step

Suppose one clone is already filled with 4, 7, 2, and its twin is still empty.

4 7 2

Step 0. One clone reads 4-7-2; its twin is empty.

Step 1 — copy across. Corresponding cells must match, so the twin takes the same digits in the same order: 4, 7, 2.

4 7 2 4 7 2

Step 1. The twin is copied cell for cell: 4-7-2.

Step 2 — the copies feed the grid. Those newly-placed digits are ordinary values now: the copied 4, 7 and 2 clear their own rows, columns and boxes, often unlocking cells far from either clone. That reach — solving one clone helps the region around the other — is what makes Clone Sudoku tick.

Solving strategy

  • Solve one clone, get the rest free. Every digit placed in one clone copies straight into its twins.
  • Work both ends. A digit forced in either clone (by its own row, column or box) transfers to all the others.
  • Mind the overlaps. If a clone and its copy share a row, column or box, the matching digits can't clash — a strong extra constraint.
  • Feed the grid. Copied digits behave like givens for their rows, columns and boxes.

Common mistakes

  • Copying in the wrong orientation. Clones match cell-for-cell in the same arrangement — line up the shapes carefully.
  • Allowing a clash. If two clones share a unit, their matching digits must not break the no-repeat rule.
  • Forgetting to transfer. Any digit placed in one clone must appear in all of them immediately.
  • Ignoring ordinary Sudoku. Clone cells still obey their rows, columns and boxes.

Can I play it here?

Not yet — Clone Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile: