How to play the 15 puzzle
- Choose the size: 3×3 (8 tiles), 4×4 (15 tiles, the classic) or 5×5 (24 tiles). The tiles start shuffled and there is a single gap.
- Tap a tile next to the gap to slide it. If you tap a farther one in the same row or column, all the ones in between move too.
- You can also swipe on the board or use the keyboard arrows: the tile on the opposite side of the gap moves in that direction.
- You win when the tiles are in order by rows, from 1 onwards, with the gap in the last square. The move counter and the time run from your first move.
A classic with math behind it
The 15 puzzle became famous in the 19th century and is still one of the best-known logic pastimes. On the 4×4 board there are more than twenty trillion ways to arrange the tiles, but only half of them can be solved by sliding: if two tiles are swapped, there is no way to fix it. That is why here the shuffle is always built so that it has a solution.
A strategy that works at any size is to solve it in layers: first complete the top row, then the left column of what remains, and so on until the last two rows and last two columns are left, which are solved by rotating tiles around the gap. Thinking a few moves ahead matters more than making many quick ones: with little practice you can solve the 3×3 in a few moves, and on the 4×4 any position can be solved in 80 moves at most.
Everything happens in your browser: nothing is sent to any server. Only your move record and your best time for each size are saved on your device.
Things to keep in mind
- Records are saved per size only in this browser: if you clear the site data, they are lost.
- Each tile that slides counts as one move, even if you move several together in a single go.
- If you change the size or start a new game, the current one is lost (the site warns you first). When you swipe on the board, the page does not scroll.
Frequently asked questions
How do you play the 15 puzzle?
You slide the tiles into the single gap until they are in order from 1 to 15, with the gap at the bottom right.
Can every shuffle be solved?
In this game, yes: the shuffle is always generated with a solution. In a puzzle put together by hand, half of the positions have no solution.
How do the tiles move on a phone?
Tap a tile next to the gap, or swipe on the board in the direction you want the tile to move.
Can I play with the keyboard?
Yes. Click the board and use the arrow keys (or W, A, S, D): the tile on the opposite side of the gap moves in the direction the arrow shows.
What is the best strategy?
Solve it in layers: first the top row, then the first column, and so on until you reach a 2×2 square at the end. Avoid undoing what you have already ordered.
Is it free? Do I need to install anything?
It is free, needs no sign-up or installation and works on phones and computers. No data is uploaded.