The sliding puzzle, online and free
The sliding puzzle, also known as the 15 puzzle or Game of Fifteen, is one of the oldest brain teasers there is: fifteen numbered tiles, one empty space, and a jumbled order to put right. There is no luck involved, just a plan and some patience.
Play it free in your browser with unlimited shuffles. Start with the classic 4×4 board, then pick Custom in the Size & level menu for bigger or smaller frames.
A famous puzzle craze
The sliding puzzle, often called the 15 puzzle, caused a craze in the United States in 1880, when people everywhere tried to slide fifteen numbered tiles back into order. Mathematicians soon proved that exactly half of all possible arrangements cannot be solved at all, because of a property called parity. Every puzzle here is generated from a solvable arrangement, so a solution always exists.
How to play here
Click or tap a tile in the same row or column as the empty space to slide it, together with any tiles between them, toward the gap. The goal is to put the numbers in order, left to right and top to bottom, with the empty space in the bottom-right corner.
A reliable method
- Solve the top row first. Place 1, 2 and 3, then bring 4 in last using the space below it.
- Then solve the left column. Place 5, 9 and 13 the same way. The puzzle is now a smaller 3×3 problem.
- Place the last two tiles of a line together. Move them into position as a pair, then rotate them into place with a short loop of moves.
- Think in loops. Most moves are small cycles of the gap around a 2×2 block. Once you see the loops, the puzzle becomes calm and methodical.
- Finish the final 2×2. The last three tiles are rotated around the gap until they line up.
Why play the sliding puzzle?
The sliding puzzle is a great test of planning: every move affects several tiles, so you must think a few steps ahead. Once you know the method, try to solve it in fewer moves. For another planning challenge, try the Tower of Hanoi or Water Sort.
How to play Sliding Puzzle
- The board holds numbered tiles and one empty space.
- Click or tap a tile next to the empty space to slide it in.
- You can also slide a whole row or column of tiles toward the gap at once.
- Put the tiles in order, left to right and top to bottom, with the gap in the bottom-right corner.
Sliding Puzzle tips
Solve the top row first, then the left column
Finish the first row and never touch it again, then the first column. The puzzle shrinks to a smaller one each time, down to a simple 2×2 at the end.
Place the last two tiles of a row together
For the end of a row, park the last tile below its spot, bring the second-to-last into the corner, then rotate both in. Trying them one by one keeps knocking the first out.
Think in loops
Moving a tile always means moving the gap around it. Cycling three tiles around a small loop is the basic move behind every advanced sequence.
Frequently asked questions
What is the 15 puzzle?
The 15 puzzle is the classic sliding puzzle with fifteen numbered tiles in a 4×4 frame and one empty space. It was a worldwide craze in the 1880s and is still a favorite brain teaser.
Is every sliding puzzle solvable?
Only half of all random arrangements can be solved. The shuffles here are always made from a solvable position, so every board can be finished.
How many moves does a 15 puzzle need?
Any 4×4 position can be solved in at most 80 single-tile moves, but finding that shortest solution is very hard. Most people need a few hundred moves.
