Fog of War Sudoku

Fog of War. Only the cells you have placed and their immediate neighbors are visible; the rest is fogged.

How to play

Fill the 9×9 grid so every row, every column, and every 3×3 box contains the digits 1 to 9 with no repeats — the classic Sudoku rule. Fog of War Sudoku adds one twist: Only the cells you have placed and their immediate neighbors are visible; the rest is fogged.

Fog of War Sudoku hides almost the entire grid: only the given clues and the cells immediately touching them start visible, while everything else sits under fog. You solve outward from those pockets of light — each correct digit you place clears the fog on that cell and the eight cells around it, exposing fresh clues to reason from. The logic underneath is ordinary 9×9 Sudoku; the twist in Fog of War Sudoku is that you never see the whole board at once, so you earn your view of it one correct placement at a time.

How to solve Fog of War Sudoku

Start from the given clues, which never fog over, and apply ordinary row, column, and box elimination to every square you can read — including still-fogged cells whose row, column, or box is already partly exposed. Place only digits you are certain of: each correct placement lifts the fog on that cell plus its eight neighbours, turning one deduction into a whole new patch of clues, so a confirmed single is worth far more than a hopeful stab. Because a wrong entry leaves the fog untouched and reveals nothing, guessing to "scout" the board is pure waste — it burns a move and buys no information. Work in chains: solve a forced single, read the newly uncovered cells for the next forced single, then repeat, letting the cleared area spread outward until separate revealed regions meet. Every Fog of War puzzle is generated so this step-by-step path always exists, which means you can finish through certainty alone and never need the entire grid uncovered at once.

Every Fog of War Sudoku puzzle is free to play in your browser — no ads, no sign-up, and it works offline.

Frequently asked questions

What is Fog of War Sudoku?

Fog of War Sudoku is a standard 9×9 Sudoku played on a grid that starts almost entirely hidden. Only the given clues and their immediate neighbours are visible; everything else is covered by fog. Each correct digit you place clears the fog around it, so the board gradually reveals itself as you solve rather than being fully shown from the start.

What are the rules of Fog of War Sudoku?

The underlying rules are ordinary Sudoku: every row, column, and 3×3 box must contain 1 to 9 once each. The extra rule is visibility — only placed cells and the eight cells touching them are shown. Placing a correct digit lifts the fog on that cell and its 3×3 surroundings, while an incorrect digit leaves the fog exactly as it was and shows you nothing new.

Do I have to guess to clear the fog in Fog of War Sudoku?

No. Every Fog of War puzzle is built so a purely logical path exists — you can always find a forced placement among the currently visible cells, and each one clears enough fog to expose the next deduction. Guessing is actually counter-productive here, because a wrong digit reveals none of the grid and simply wastes a move.