Singles and direct techniques

The simplest logical placements: a single candidate or a single cell for a digit, plus direct elimination techniques that immediately reveal a placement.

A selected Sudoku cell with only candidate 8 remaining

Naked Singles

A cell with exactly one candidate remaining.

Candidate 8 highlighted as the only possible 8 in a Sudoku box

Hidden Single

The only cell for a digit within a row, column or box.

Candidate 1 confined to one Sudoku box column, eliminating three other candidate 1s

Direct Pointing

A pointing elimination that immediately creates a placement.

Candidate 1 confined to one Sudoku box within a column, eliminating three other candidate 1s

Direct Claiming

A claiming elimination that immediately creates a placement.

A hidden pair of candidates 2 and 8 reveals a placed 7 in the same Sudoku column

Direct Hidden Pair

A hidden pair whose eliminations immediately reveal a digit.

Direct Hidden Triplet

A hidden triplet that directly unlocks a placement.

From Sudoku singles to direct placements

Naked Singles and Hidden Singles are the core placement techniques in candidate-based Sudoku solving. A Naked Single is a cell with only one candidate left. A Hidden Single is different: a digit may share its cell with other candidates, but it has only one possible position within a row, column or box. Scanning both cells and houses is the reliable way to spot them.

Direct techniques combine an elimination pattern with the single it immediately creates. Direct Pointing and Direct Claiming use the interaction between a box and a row or column. Direct Hidden Pairs and Direct Hidden Triplets restrict two or three digits to the same number of cells, remove the other candidates there, and reveal a forced placement. Learning the complete logical sequence—pattern, elimination, then placement—builds the precision needed for harder Sudoku techniques.

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