Sliding puzzle: put the numbered tiles in order

The classic sliding puzzle: numbered tiles, one gap, and the job of sliding them back into order. This page plays the 15 puzzle on a 4×4 board, and the 8 and 24 puzzles are one click away. Free, with no app, no sign-up and no interstitial before play; it works offline, plays from the keyboard, and every shuffle is guaranteed solvable.

How to play the sliding puzzle

1. The board holds numbered tiles and one empty space, the gap.
2. Tap or click a tile next to the gap to slide it in. Tapping a tile further along the same row or column slides the whole run at once.
3. On a keyboard, an arrow key slides the tile next to the gap in that direction; Tab and Enter pick and slide a specific tile.
4. Each tile that moves one cell counts as one move.
5. Finish with the tiles in reading order, 1 in the top-left corner, and the gap in the bottom-right.
6. Stuck? A hint highlights a tile to slide next.

Sliding puzzle strategy: solve it row by row

Trying to move every tile towards home at once goes in circles. The reliable method, which works on every size, is to finish one row, then one column, and never disturb them again, until only a 2×2 corner is left.

Place the top row, saving the last two tiles

On the 15 puzzle, put 1 and 2 in place first; that is easy because the rest of the board is free. Tiles 3 and 4 need a trick. Park 4 in the cell where 3 belongs, bring 3 directly below it, then move the gap round so 4 slides right and 3 slides up behind it. Trying to place 3 first and then 4 almost always knocks 3 out again.

Repeat for the left column

With the top row fixed, solve the left column the same way: 5 and 9 first in place, then 13 using the same pairing trick sideways. Now the 15 puzzle has become an 8 puzzle on the lower-right 3×3, with tiles 6, 7, 8, 10, 11, 12, 14 and 15.

Finish on a 2×2 corner

Keep peeling off the top row and left column of whatever is left. At the end, three tiles and the gap share a 2×2 corner, and the only thing they can do is rotate. Turn them in one direction until they fall into place; the position is always solvable, so they will.

Move the gap, not the tile

The key habit is to plan where the gap goes. To push a tile left, the gap must first be on its left side; to get it there without disturbing your finished rows, route the gap around the tile. On larger boards this is most of the work.

Why every shuffle here can be solved

If you lay the tiles out at random, exactly half of all arrangements cannot be solved by sliding. Every slide swaps the gap with a tile, and a hidden count of out-of-order pairs, called parity, changes in a fixed way with each move. Arrangements with the wrong parity, such as a finished board with 14 and 15 swapped, can never be reached.

So we never lay tiles out at random. Each shuffle starts from the solved board and plays random legal moves, never undoing the previous one: 108 moves on 3×3, 256 on 4×4 and 500 on 5×5. Whatever you get, it can be solved, because it was made by sliding.

How the hint works

The hint searches for a shortest solution from the current position. When it finds one it marks the first tile of that path as the Optimal move. The 3×3 search almost always finishes; on 4×4 and 5×5 it only succeeds near the end of a game, and otherwise the hint marks the Closest move, the slide that brings the tiles nearest to home.

The 15 puzzle craze of 1880

The 15 puzzle appeared in the United States in the 1870s and became a craze in 1880, spreading across America and Europe as a wooden box of fifteen numbered blocks. Newspapers wrote about it, and people played it at work and at home.

Mathematicians soon explained why some positions could not be solved: in 1879 it was proved that exactly half of all arrangements are out of reach. The smaller 8 puzzle later became a standard example in computer science for search methods, which is exactly what our hint uses.

Daily, stats and printables

The move counter and timer start with your first slide, and the timer pauses when you switch tabs. Stats are kept per board size in your browser: played, won, win rate, best and average time. Each of the three boards keeps its own records.

Undo and redo are unlimited. The first two hints in each puzzle are free; if ads are switched on later, further hints offer a short ad or a 30-second wait. Every shuffle has a puzzle code such as A7K3Q, so ?p= replays the same start, and Share result copies your time and moves. There is no daily sliding puzzle and no printable version.

Plays anywhere, no app, no account

Tiles slide with a tap on a phone, a click on a computer or the arrow keys, and each tile is labelled with its number and position for screen readers. Tidy Puzzles runs entirely in your browser: there is no app to install, no account to create and no interstitial before you can play. After the first visit the game also works offline, because each puzzle is generated on your device from a seed. Every board can be played with the keyboard alone, on a phone or a desktop, and your stats and unfinished puzzles stay in this browser rather than on a server.