How to analyse a Sudoku safely
Enter 81 cells using digits for givens and zeroes or dots for blanks. First, the validator checks whether a filled digit repeats in its row, column, or 3x3 box. It also flags an empty cell with no legal candidate, because that usually means an earlier entry is wrong.
Once the position is consistent, the teaching engine builds a fresh candidate map. It searches for deductions in increasing complexity: singles first, then locked candidates, pairs, triples, fish patterns, and an XY-Wing. A move is presented only when the current board proves it.
Candidate analysis versus answer lookup
An answer lookup tells you what belongs in a square. Candidate analysis tells you why. For each empty cell, SudokuIQ removes digits already present in the same row, column, and box. The remaining digits are possibilities—not promises. A candidate becomes a placement only when a technique proves it.
This distinction matters when learning. If a cell allows 2 and 7, choosing either digit is still a guess. You may instead find that 7 has only one possible home elsewhere in the row, or that a pair removes 2 from a neighbouring square.
What the analyzer deliberately refuses to do
The Logic Lab does not upload a puzzle, silently replace your entries, or label a stored answer as reasoning. If no supported technique is provable, it says so. That makes the tool useful for checking your own work without turning every difficult position into an unexplained reveal.