How to Solve Lights Out (the Trick That Always Works)
Lights Out looks like it should be easy. It’s a grid of lights, you press one, it flips along with the lights above, below, left and right of it, and you’re trying to get the whole board dark. Then you press a few and the board looks worse than when you started.
There’s a method that works on every board that can be solved, and you don’t need any math to use it. It’s called light chasing. If you just want the answer to the puzzle in front of you, my free Lights Out solver will show you exactly which lights to press. If you want to know how to do it yourself, read on.
Two rules that make it solvable
The order doesn’t matter. Every press flips the same lights no matter when you do it, so pressing A then B gives the same board as B then A.
Pressing a light twice undoes it. So you never need to press anything more than once. A solution is just a set of lights to press, one time each.
Those two rules are why light chasing works.
Light chasing, step by step
- Look at the top row. For every light that’s on, press the light directly below it in the second row. That turns the top-row light off (and messes with the second row, which is fine).
- Now the top row is dark. Do the same thing with the second row: for every light that’s on, press the one below it in the third row.
- Keep going down until you reach the bottom row. Every row above it is now dark.
- Whatever is still lit in the bottom row tells you what to press in the top row. Look it up in the table below, press those top-row lights, and then chase the lights down one more time. The board goes dark.
The 5×5 table (the original handheld size)
Read each row left to right. 1 means lit (or press), 0 means dark (or leave it alone).
| Bottom row still lit | Press in the top row |
|---|---|
| 00111 | 00010 |
| 01010 | 10010 |
| 01101 | 10000 |
| 10001 | 11000 |
| 10110 | 00001 |
| 11011 | 00100 |
| 11100 | 01000 |
If your bottom row doesn’t match any line in the table, that board can’t be solved. That’s not you doing it wrong. On a 5×5 grid, only 1 in 4 of all possible boards has a solution at all, and the other 3 can’t be finished no matter what you press. A board that came from the game itself will always be solvable, so if you’re stuck on one you typed in by hand, check that you copied it right.
Other sizes
- 3×3: every board can be solved, and each has exactly one solution. 3×3 solver
- 4×4: only 1 in 16 boards can be solved, but here’s the nice part: if it can be solved, chasing the lights down is all you need. The bottom row comes out dark on its own. 4×4 solver
- 5×5: 1 in 4 boards can be solved, each has 4 different solutions, and the hardest ones take 15 presses. 5×5 solver
- 6×6 and 7×7: every board can be solved, and each has exactly one solution. The full lookup tables would be 63 and 127 lines long, but you don’t need them: a short table with one line per bottom light does the same job. It’s on the 6×6 and 7×7 solver pages.
Stuck in a video game?
A lot of games have this same puzzle built in and call it something else: a tile flip puzzle, a light switch puzzle, a flip switch puzzle. Sometimes pressing a tile flips a different set of neighbors, like the diagonals, or a whole row and column. The solver handles those too. Press one tile in your game, see which ones change, and pick the matching pattern under “What happens when you press one?” It also handles grids that aren’t square and tiles that cycle through three colors.
Want to practice?
I built a daily version called Porchlight. Every night there’s a new street of porch lights to turn off, easy on Monday and hardest on Saturday, with a twist on Sunday. Light chasing works on the weekday boards (on the 6×6 ones, the table on the 6×6 page gets you through the last step), but not on the Sunday twists, and it’ll rarely get you par.
