All Sudoku Variants
9×9 · Constraint

Non-Consecutive Sudoku

A single global rule: no two orthogonally adjacent cells may contain consecutive digits.

1 4 7 2 9 5 3

An example Non-Consecutive puzzle (no marks): touching cells never differ by 1 — every orthogonal neighbour here differs by at least 2.

Non-Consecutive Sudoku adds a single, board-wide rule and draws no marks at all: no two orthogonally adjacent cells may contain consecutive digits. Wherever two cells touch side by side — up, down, left or right — their values must differ by at least 2. It looks gentle, but that quiet rule threads eliminations through the whole grid.

The rule: touching cells jump by two or more

Take any filled cell. Each of its four orthogonal neighbours is forbidden from being one higher or one lower. A 5 in the middle of the grid, for example, blocks a 4 and a 6 in the cell above, below, left and right of it — though diagonally, consecutive digits are perfectly fine.

5 4,6 4,6 4,6 4,6

A 5 forbids 4 and 6 in its four orthogonal neighbours. Diagonal neighbours are unaffected.

What each digit forbids

Most digits knock two values out of every touching cell — a 5 removes 4 and 6, a 3 removes 2 and 4. The extremes are looser: a 1 only forbids a 2 (there is no 0), and a 9 only forbids an 8. That makes the middle digits the more powerful clues and the 1s and 9s slightly freer neighbours. Note too that 5 can never touch a 4 or a 6, so long runs of near-middle digits are heavily constrained.

2 5 3 8 6 9 4 7 1

A legal row: 2-5-3-8-6-9-4-7-1 — every neighbouring pair differs by 2 or more.

Where it shows up

The non-consecutive rule is a building block of the famous Miracle Sudoku, where it combines with anti-king and anti-knight constraints to solve a grid from just two given digits. On its own it is subtler, but the same idea drives it: every placement quietly forbids its neighbours from the two values next to it, and those small bans accumulate into singles.

Solving strategy

  • Sweep neighbours on every placement. After writing a digit, cross its two consecutive values out of all four orthogonal neighbours.
  • Lean on the middle digits. A 4, 5 or 6 removes two candidates from each neighbour; a 1 or 9 removes only one.
  • Watch runs. Adjacent cells must zig-zag by 2+, so a line can never step 4-5 or 6-5 — use that to rule out sequences.
  • Combine with the box. The neighbour bans often leave a box digit only one legal home.

Common mistakes

  • Including diagonals. Only the four orthogonal neighbours are constrained; a diagonal 4 next to a 5 is allowed.
  • Forgetting the extremes. A 1 forbids only a 2 and a 9 only an 8 — do not remove a phantom 0 or 10.
  • Reading it as "no repeats". The rule is about consecutive values, not equal ones — repeats are already banned by ordinary Sudoku.
  • Dropping the normal rules. Rows, columns and boxes still need 1–9; the non-consecutive rule is an extra layer.

Can I play it here?

Not yet — Non-Consecutive 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: