What is an Akari solver?
An Akari solver is a tool for completing Light Up puzzles, the Japanese logic puzzle where bulbs illuminate white cells and black cells act as walls. Enter the wall layout, add any numbered black clues, and the solver can find a valid bulb placement.
This page is written for searches such as Akari solver, Light Up puzzle solver, Akari puzzle solver online, Light Up solver, Akari answers, Akari helper, Light Up hints and next move Akari solver. The tool is designed for both checking a finished puzzle and learning the logic one step at a time.
- Solve an Akari puzzle from a book, newspaper, app or printable grid.
- Check whether your current bulb and marker placements are still possible.
- Reveal one next logical move without showing the whole solution.
- Test a custom Light Up puzzle for validity and uniqueness.
How to use this Light Up puzzle solver
Choose a grid size, then use clue mode to build the puzzle. Click a cell to cycle through white, black wall, 0, 1, 2, 3 and 4. Numbered black cells count only the four orthogonally adjacent cells, not diagonals.
Switch to bulb mode when you want to enter a partial solve. Click a white cell to cycle blank, bulb and marker. Press Solve for the completed grid, Check to test your current work, or Next move to show a single deduction with a short explanation.
- Use 5x5 or 6x6 for quick hand-entered puzzles.
- Use 7x7 to 12x12 for larger Light Up grids.
- A marker means the cell is known not to contain a bulb.
- Apply move updates the grid only after you decide to accept the hint.
- Clear marks keeps the wall and clue layout while removing bulbs and markers.
Akari rules used by the solver
The solver uses the standard Akari rules, also known as Light Up rules. A bulb lights its own square and every white square it can see horizontally and vertically until a black wall blocks the beam.
Every white cell must be lit. Two bulbs may not see each other along an uninterrupted row or column. A numbered black cell must have exactly that many bulbs in the four neighbouring cells above, below, left and right.
- Bulbs can be placed only in white cells.
- Black walls stop light.
- Blank black walls have no bulb count requirement.
- Numbered walls count adjacent bulbs only.
- A finished puzzle has no dark white cells and no bulb conflicts.
Next move logic and Akari strategies
The Next move button looks for human-style deductions first. If a clue is already satisfied, every other adjacent white cell becomes a marker. If a clue still needs the same number of bulbs as it has open neighbours, all of those neighbours become bulbs.
The helper also uses corridor logic. A bulb rules out every visible cell in its row and column. If a dark cell has only one legal place from which it can be lit, that position is forced. These rules cover many beginner and intermediate Akari strategy moments without guessing.
- 0 clues mark every adjacent white cell as impossible.
- 4 clues usually force every adjacent white cell to be a bulb.
- Satisfied clues create markers around them.
- Unlit cells with one possible light source force a bulb.
- Bulb sight lines remove other bulb candidates in the same corridor.
Why an Akari puzzle may have no solution
An Akari puzzle becomes impossible if a numbered wall has too many adjacent bulbs, if two bulbs can see each other, or if a white cell cannot be lit by any legal bulb. A clue can also become impossible when too many of its neighbouring cells have been marked as not bulbs.
A custom puzzle may also have multiple solutions. Published Light Up puzzles normally aim for a unique answer, but a grid with too few numbered clues or walls can allow several valid bulb layouts. The solver reports that case so you know whether the puzzle is fully constrained.