What is a Nurikabe solver?
A Nurikabe solver is an online tool that completes a Nurikabe puzzle from its numbered island clues. Nurikabe is the Japanese island-and-wall logic puzzle where white islands must match their clue sizes and all black wall cells must form one connected shape.
This page is built for searches such as Nurikabe solver, Nurikabe puzzle solver, online Nurikabe solver, free Nurikabe solver, Nurikabe helper, Nurikabe answers, Nurikabe hints, Nurikabe strategy and how to solve Nurikabe. It can solve the full grid, check a partial position or show one next logical move.
- Solve a Nurikabe puzzle from a book, app, newspaper or printable sheet.
- Enter only the numbered island clues, or add walls and open cells you already know.
- Check whether your current Nurikabe grid still has a valid solution.
- Reveal one wall or one island cell without showing the entire answer.
How to use this Nurikabe solver
Choose a grid size, then click Create grid. In clue mode, click a cell and type the island number. Press Backspace or Delete to remove a clue. In marks mode, click a non-clue cell to cycle through wall, open island cell and blank.
Press Solve to complete the puzzle. Press Check if you only want to know whether the current clues and marks are still possible. Press Next move for a single highlighted deduction, then Apply move if you want to add it to the board.
- Use clue mode for the printed numbers.
- Use wall marks for black cells you have already proved.
- Use open marks for cells you know belong to some island.
- Leave uncertain cells blank.
- Start with the example puzzles if you want to see the input style.
Nurikabe rules used by the solver
The solver follows standard Nurikabe rules. Every number is part of a white island, and that island must contain exactly the number of cells shown by the clue. Two different islands may touch diagonally, but they may not share an edge.
All black cells form the wall. The wall must be one connected orthogonal area, and a completed solution may never contain a 2 x 2 block of black wall cells.
- Each island contains exactly one clue.
- Each island size equals its clue number.
- Different islands cannot touch by an edge.
- All wall cells connect into one continuous wall.
- No 2 x 2 square can be entirely wall.
Next move logic and Nurikabe strategy
The Next move button begins with common human Nurikabe strategies. A 1 clue is already complete, so its neighbouring cells become wall. A completed island must be surrounded by wall. A cell that would connect two different clue islands also has to become wall.
The solver also watches for forbidden 2 x 2 wall blocks. If three cells in a 2 x 2 square are already wall, the fourth cell must stay open. When local logic is not enough, the helper searches every valid completion it can find and highlights a cell that is forced in all of them.
- Completed island: surround it with wall.
- Separate islands: block cells that would merge two clues.
- No 2 x 2 walls: force open cells that prevent a black square.
- Reachability: a white cell must be able to connect to a clue.
- Forced cell: every valid solution agrees on wall or island.
Why a Nurikabe puzzle can be impossible or ambiguous
A Nurikabe puzzle becomes impossible when an island grows too large, two numbered islands merge, the wall is split apart, or a 2 x 2 wall block is forced. A single wrong wall can also stop an island from reaching its required size.
A puzzle is ambiguous when more than one finished grid satisfies the same clues. Published Nurikabe puzzles usually aim for one unique solution so each step can be justified by logic rather than guessing.