Can the wall be split into pieces?

No. Every shaded cell must connect to every other one through shaded cells side by side.

Can an island have no number?

No. Every unshaded area holds exactly one number, and its size equals that number.

What does the dot mean?

A dot is a note that a cell stays unshaded. It isn’t needed for the answer, but marking island cells you’re sure of keeps the counting straight.

Does every Nurikabe have one solution?

Every Nurikabe on this site does. Each one is checked by a solver that tries every possible island shape.

How big are the puzzles?

The daily Nurikabe is 8×8. Practice puzzles come in 5×5, 7×7 and 9×9.

How to play Nurikabe (Islands in the Stream): rules, tips and FAQ

Watch one get solved

DemoStep through a small Nurikabe being solved. Each move follows from one rule, and the ring shows which clue it comes from.A 1 is an island all by itself, so every cell beside it is wall. Shade the three cells around the 1 at the top.Same for the 1 in the bottom-left corner: shade the cell above it and the cell to its right.Every unshaded cell belongs to a numbered island. Each 2 can only reach the cells right beside it, and three cells aren’t beside either 2. Nothing can reach them, so they’re wall.The wall can’t fill a 2×2 block. On the right, three cells of a square are shaded, so the fourth, just above the bottom 2, stays unshaded. Dot it.That dot sits next to the bottom 2, so it’s the 2’s second cell. The island is full, so wall it off: shade the bottom-right corner.All the wall must join into one piece. The shaded cells in the bottom-left can only get out through the cell beside the 2 on the left. Shade it, and the 2 takes the top-left corner. Solved!

Using the board

Tap a cell to shade it. Tap again for a dot, which means “this stays unshaded”. A third tap clears it.

Drag across cells to shade or dot several at once. Numbered cells can’t be shaded.

A number turns grey once its island is walled off at exactly the right size.

Settled mistakes turn red: a 2×2 block of shading, an island walled off too small, or dots that join two numbers.

What is Nurikabe?

Nurikabe is about building a wall. Every number marks an island of unshaded cells exactly that size, and every island holds exactly one number. Everything else is shaded, and the shaded cells must join into one connected wall that never covers a 2×2 block.

The puzzle comes from Nikoli and is named after the nurikabe, a spirit from Japanese folklore that appears as an invisible wall blocking travelers at night. In English it’s sometimes called Islands in the Stream.

How to start a Nurikabe

Shade around the 1s: each is an island on its own, so all four neighbors are wall. Then shade any blank cell that touches two different numbers, since it would join two islands.

Next, find cells no island can reach. If a cell is further from every number than that number’s island could stretch, it has to be wall.

From there, alternate between the two big rules. The wall can’t form a 2×2 block, so when three cells of a square are shaded, the fourth is unshaded. And the wall must stay in one piece, so a section of wall with only one way out has to extend that way.

Common mistakes

Islands can touch diagonally, but never side by side. If two islands would meet edge to edge, a wall cell belongs between them.

It also helps to count. The number of shaded cells is the grid size minus the total of all the numbers, which tells you how much wall is still to place.

Questions

Can the wall be split into pieces?: No. Every shaded cell must connect to every other one through shaded cells side by side.
Can an island have no number?: No. Every unshaded area holds exactly one number, and its size equals that number.
What does the dot mean?: A dot is a note that a cell stays unshaded. It isn’t needed for the answer, but marking island cells you’re sure of keeps the counting straight.
Does every Nurikabe have one solution?: Every Nurikabe on this site does. Each one is checked by a solver that tries every possible island shape.
How big are the puzzles?: The daily Nurikabe is 8×8. Practice puzzles come in 5×5, 7×7 and 9×9.

Play today’s Nurikabe Solving techniques

How to play Nurikabe

The rules