How to Solve Hashi: Where to Start

Niels Glodny · 3 November 2026

Almost every move in Hashi comes from counting. Pick an island, count how many bridges its neighbours can still take, and compare that with its number. If they match, or nearly match, some bridges are forced. This article covers the counting that solves most small boards, then works through a full puzzle. If you have not played before, read the rules first.

Count the neighbours

A neighbour is the nearest island in a straight line up, down, left or right. An island has at most four. Each neighbour can take at most two bridges from it, so an island with two neighbours can hold at most four bridges, one with three neighbours at most six, and so on.

Islands that are full

When the number is exactly twice the number of neighbours, every direction gets a double bridge. That means a 2 with one neighbour, a 4 with two, a 6 with three or an 8 with four. An island with only one neighbour is also settled at once, whatever its number: all its bridges go there.

It is the number of neighbours that matters, not where the island is. Corners and edges come up often because islands there have fewer directions, but an island in the middle of the board with only two neighbours works the same way.

Islands that are nearly full

When the number is one less than twice the neighbours, every direction gets at least one bridge. That means a 3 with two neighbours, a 5 with three or a 7 with four. Even if every other direction got a double bridge, they would be one short, so no direction can be left empty. Put a single bridge in each direction. The last bridge comes later.

Neighbours that cannot take much

A neighbour does not always have room for two bridges. A 1 can only ever take one. An island that already has all its bridges takes no more, and it stops counting as a neighbour. Once you start placing bridges, recount with these limits and new forced moves appear.

Placed bridges also block. A bridge removes every connection that would cross it, so an island next to a long bridge may have lost a neighbour.

Do not cut off a group

Joining two 1s fills both of them, and the pair can never connect to anything else. So two 1s are never joined to each other, unless they are the only islands on the board. The same goes for a double bridge between two 2s.

A puzzle, step by step

Here is the 6×6 puzzle from the rules page. Every move follows from the ideas above. The ringed islands are the ones each step looks at.

Step 1. Four islands are settled straight away. The 4 in the top-left corner has two neighbours, so it gets two double bridges. The same holds for the 4 in the bottom-left corner and for the 4 on the right edge, which has nothing to its left. The 1 has a single neighbour, the 2 below it.

Step 2. The 5 on the left edge now has four bridges and needs one more. Up and down are taken, so the last one goes right, to the 4 in the middle. The 3 in the top-right corner has two bridges from below and needs one more, which can only go left. The 3 in the bottom-right corner works the same way.

Step 3. The 4 at the top of the middle column has three bridges, and its last one can only go down. The same is true for the 4 at the bottom of that column, which sends its last bridge up. The 4 in the middle now has three bridges, from the left, above and below, so its fourth goes right to the 2. That gives the 2 its second bridge, and the puzzle is solved.

When you are stuck

Go round every island that is not yet full and count again, using the limits above: full neighbours do not count, a neighbour that needs one more bridge can take only one, and a placed bridge blocks the ones it crosses. Then look at groups of connected islands that are close to being closed off.

Larger boards need a few more ideas, such as thinking about whole groups and following a guess to a contradiction. They are in Advanced Hashi techniques. In the game, the hint button points at a wrong or missing bridge. It takes ten seconds.