Forcing Nets

Extreme Reference only

Forcing Chains generalized into a branching tree instead of a single line — every branch from an assumption is followed, and any conclusion every branch agrees on holds.

The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.

First colour in the chain
Cells that establish the pattern
Where the conclusion lands
Candidate ruled out

How it works

Assume A1 = 3. Unlike a plain Forcing Chain (one line of dominoes), that assumption branches: it forces E1 ≠ 3 AND E2 ≠ 3 independently, which can each cascade differently.
If every branch of the resulting net — no matter how it forks — ends up agreeing E5 can't be 6, that elimination holds regardless of which path the truth actually takes.

Play a Sudoku that needs this technique →