What are the rules of Nurikabe?

Each orthogonally connected land island contains exactly one numbered clue and exactly that many cells, including the clue. All sea cells connect through their sides, and no 2 × 2 block can be entirely sea. Separate islands may touch diagonally.

How do I mark a cell as land or sea?

Choose Land, Sea or Unknown, then activate a non-clue cell. A dot marks land, a dark circle marks sea and a question mark marks an unknown cell. Clue cells always stay land. Tab and arrow keys navigate the board; Enter or Space applies the selected state.

Are these puzzles uniquely solvable?

Yes. The collection contains 20 original base puzzles: eight at 5 × 5 and four each at 6 × 6, 7 × 7 and 8 × 8. Every base puzzle and each of its eight rotations or reflections is exhaustively checked to have exactly one solution. The tool does not claim a measured difficulty rating.

Does each seed create a different puzzle?

A seed deterministically chooses a base puzzle and a rotation or reflection from the finite collection. Different seeds can select the same puzzle. A previously opened puzzle family remains practice during that visit, including under a different seed or orientation.

What does Check current marks tell me?

It reports rule violations proved by your current marks, including joined clues, oversized islands, isolated unnumbered land, disconnected sea and 2 × 2 sea blocks. Unknown cells remain incomplete, and areas that could still connect are described as undetermined. A check makes an unfinished challenge practice only.

Can I undo a mark or resume a saved puzzle?

Undo restores the previous cell state and change count. The browser saves settings, clues and marks when local storage is available; saved progress is checked against the original template and recorded changes before it resumes. Undo and resumed puzzles remain playable as practice.

How do the seeded challenges work?

Finish a fresh 5 × 5 puzzle without checks, answers or undo to unlock a challenge link, native sharing and a PNG result card. The score counts successful cell-state changes, including corrections; lower is better. The recipient starts the same puzzle and can compare and reshare their own result. Scores are self-reported.

Can I print a puzzle without the answer?

Print puzzle opens a clean board containing only the original clues, excluding your entered marks. Print puzzle and answer key adds the solution on a separate page. Requesting an answer key makes an unfinished challenge practice only; opening a print dialog does not confirm a saved PDF.

What are useful first steps in a Nurikabe puzzle?

A clue of 1 is already a complete island, so each side-adjacent cell must be sea. When any island reaches its clue size, its remaining side neighbors must be sea so it cannot grow or join another clue. Keep sea connected through sides and avoid a 2 × 2 sea block; diagonal land contact is allowed. Check current marks reports proved violations and incomplete areas rather than automatically solving the board. Requesting a check during an unfinished challenge makes it practice.

What is a Nurikabe puzzle?

It is a logic puzzle in which numbered land islands sit in one connected sea. The number is the exact size of its island, including the clue cell, and separate islands cannot join through their sides. The sea must remain connected and contain no solid 2 × 2 sea square. This page offers the island-and-sea puzzle, with online marking and clean printing.

Nurikabe Puzzles

Build numbered islands and one connected sea. Choose a 5 × 5 through 8 × 8 board and a seed, then mark non-clue cells Land, Sea or Unknown. Each island must have one clue and exactly that many cells; sea connects through sides and cannot form a 2 × 2 block. Check current marks, undo or reveal an answer for practice, and print a clean clue board. Seeds select and transform 20 original templates, so different seeds can repeat a puzzle.

Original verified-unique puzzles · land, sea and unknown marks

Choose a puzzle5 × 5 to 8 × 8

Grid sizePuzzle seed

Seed: whole number from 0 to 4294967295.

The collection has 20 original base puzzles: eight at 5 × 5 and four at each larger size. A seed selects a base puzzle, rotation and reflection. Different seeds can repeat a puzzle.

Rule feedbackOnly on request

Island rule
Every connected land island has one clue and exactly the number of cells shown. Separate islands can touch diagonally.

Sea rule
Sea cells connect through their sides to form one area. No 2 × 2 square may be entirely sea.

Every base puzzle and its rotations/reflections has exactly one solution, verified by exhaustive tests. No difficulty rating is inferred from grid size.

Choose a grid and seed, then start a puzzle.

Grid: Not started

Board status: Not started

Cell changes: 0

Solution count: Choose puzzle

Worked rules

Two clues connectedOne land island contains both
Invalid. Each island must contain exactly one clue.
Four sea cellsAll four form a 2 × 2 square
Invalid. At least one of them must be land.
Diagonal land contactLand corners touch, sides do not
Allowed. The sea still has to connect through sides.

Accuracy. Every offered puzzle is a seeded selection and rotation or reflection of one of 20 original templates from 5 × 5 to 8 × 8, each independently checked to have exactly one solution. Each orthogonally connected land island has one clue and exactly that many cells; the sea is one nonempty connected area with no 2 × 2 sea block, and diagonal land contact is allowed. Feedback checks the current marks, with unknown cells treated as incomplete rather than solved.

Common questions

What are the rules of Nurikabe?: Each orthogonally connected land island contains exactly one numbered clue and exactly that many cells, including the clue. All sea cells connect through their sides, and no 2 × 2 block can be entirely sea. Separate islands may touch diagonally.
How do I mark a cell as land or sea?: Choose Land, Sea or Unknown, then activate a non-clue cell. A dot marks land, a dark circle marks sea and a question mark marks an unknown cell. Clue cells always stay land. Tab and arrow keys navigate the board; Enter or Space applies the selected state.
Are these puzzles uniquely solvable?: Yes. The collection contains 20 original base puzzles: eight at 5 × 5 and four each at 6 × 6, 7 × 7 and 8 × 8. Every base puzzle and each of its eight rotations or reflections is exhaustively checked to have exactly one solution. The tool does not claim a measured difficulty rating.
Does each seed create a different puzzle?: A seed deterministically chooses a base puzzle and a rotation or reflection from the finite collection. Different seeds can select the same puzzle. A previously opened puzzle family remains practice during that visit, including under a different seed or orientation.
What does Check current marks tell me?: It reports rule violations proved by your current marks, including joined clues, oversized islands, isolated unnumbered land, disconnected sea and 2 × 2 sea blocks. Unknown cells remain incomplete, and areas that could still connect are described as undetermined. A check makes an unfinished challenge practice only.
Can I undo a mark or resume a saved puzzle?: Undo restores the previous cell state and change count. The browser saves settings, clues and marks when local storage is available; saved progress is checked against the original template and recorded changes before it resumes. Undo and resumed puzzles remain playable as practice.
How do the seeded challenges work?: Finish a fresh 5 × 5 puzzle without checks, answers or undo to unlock a challenge link, native sharing and a PNG result card. The score counts successful cell-state changes, including corrections; lower is better. The recipient starts the same puzzle and can compare and reshare their own result. Scores are self-reported.
Can I print a puzzle without the answer?: Print puzzle opens a clean board containing only the original clues, excluding your entered marks. Print puzzle and answer key adds the solution on a separate page. Requesting an answer key makes an unfinished challenge practice only; opening a print dialog does not confirm a saved PDF.
What are useful first steps in a Nurikabe puzzle?: A clue of 1 is already a complete island, so each side-adjacent cell must be sea. When any island reaches its clue size, its remaining side neighbors must be sea so it cannot grow or join another clue. Keep sea connected through sides and avoid a 2 × 2 sea block; diagonal land contact is allowed. Check current marks reports proved violations and incomplete areas rather than automatically solving the board. Requesting a check during an unfinished challenge makes it practice.
What is a Nurikabe puzzle?: It is a logic puzzle in which numbered land islands sit in one connected sea. The number is the exact size of its island, including the clue cell, and separate islands cannot join through their sides. The sea must remain connected and contain no solid 2 × 2 sea square. This page offers the island-and-sea puzzle, with online marking and clean printing.

Every offered puzzle is a seeded selection and rotation or reflection of one of 20 original templates from 5 × 5 to 8 × 8, each independently checked to have exactly one solution. Each orthogonally connected land island has one clue and exactly that many cells; the sea is one nonempty connected area with no 2 × 2 sea block, and diagonal land contact is allowed. Feedback checks the current marks, with unknown cells treated as incomplete rather than solved.