Sliding Puzzle
Shuffling today’s tiles…
Play the 15 puzzle online, free
The sliding number puzzle, better known as the 15 puzzle, is fifteen numbered tiles in a 4×4 frame with one empty space. Slide tiles into the gap until they read 1 to 15 in order, with the gap in the bottom-right corner. Today’s board is the same for everyone, and it’s scrambled with legal moves only, so it can always be solved. Want a warm-up? The 3×3 board (the “8 puzzle”) is quicker; 5×5 (the “24 puzzle”) is a proper workout.
How to solve a sliding tile puzzle
- Solve the top row first. Place 1, 2 and 3 in order. For the last tile of the row (4), park it below its target, then bring 3 and 4 in together with a small rotation.
- Then the second row the same way (5 to 8). Once two rows are fixed, never disturb them again.
- Finish the last two rows column by column. Place 9 and 13 as a pair, then 10 and 14, then cycle the final three tiles around the gap.
Rotating a 2×2 block of three tiles plus the gap is the core move: it shifts tiles around a loop without disturbing anything else.
Why some sliding puzzles can’t be solved
Pop two tiles out of a real 15 puzzle and swap them, and you have a one-in-two chance of making it impossible. The rule comes from counting inversions, pairs of tiles that sit in the wrong order. On a 4×4 board a position is solvable exactly when inversions plus the gap’s row (counted from the bottom) is odd. Every legal slide keeps that total’s odd-or-even status, so no amount of sliding can cross over. Try it below.
0 inversions (pairs of tiles in the wrong order, reading left-to-right, top-to-bottom)
1 row of the gap, counted from the bottom
0 + 1 = 1, which is odd → solvable
Tap a tile next to the gap to slide it, or tap two tiles to swap them by hand. Watch the verdict.
Questions players ask
What is the 15 puzzle?
A sliding tile puzzle with fifteen numbered tiles and one gap in a 4×4 frame. It became a craze in the United States in 1880.
Is every sliding puzzle solvable?
No. Exactly half of all arrangements are impossible. The daily board here is always scrambled by legal slides, so it is always solvable.
What is the fewest number of moves?
Every 15 puzzle position can be solved in 80 single-tile moves or fewer, a result proved by computer search in the 1990s. Humans typically take 100 to 300.
Can I play with a keyboard?
Yes. Focus the board and use the arrow keys; each press slides a tile in that direction into the gap.
Do 3×3 and 5×5 boards count toward my streak?
Yes. Solving any size today marks the sliding puzzle done on your rack.