Trusted Pure Sudoku logic

The solver uses the same engine that powers our playable boards, so every answer is unique and double-checked
for validity before it is shown.

• Highlights conflicts instantly so you can fix typos before solving.
• Marks the digits you entered in a lighter tone and colors solved cells in Pure Sudoku blue.
• Works great on phones—tap a cell, then tap a keypad number to fill it.

When to use a Sudoku solver

Solvers are perfect when you want to check your work, rescue a nearly-finished newspaper puzzle, or verify that a
friend’s custom board is solvable before spending time on it. If you love the challenge, try solving manually
first and keep this tool as a safety net.

• Scan a paper board row by row and fill in the matching squares above.
• Use the Clear board button to reset between puzzles or after printing a solution.
• On iPhone, tap a cell and use the keypad so you never need to open the keyboard.
• Need hints instead of a full solve? Jump into the how to play guide for step-by-step help.

How the Pure Sudoku solver works

We run a constraint-driven backtracking algorithm that mirrors human logic before brute force. The solver checks
rows, columns, and boxes for conflicts, validates that the clues you entered produce exactly one solution, and
then fills the empty cells.

• Every puzzle is solved locally in your browser—nothing is uploaded.
• Conflicts are highlighted in red so you can correct mistakes fast.
• If a puzzle has no solution, you will see a friendly error instead of a blank page.