Fifteen is the classic sliding-tile puzzle: fifteen numbered plaques in a four-by-four tray with one empty socket. Slide them until they read 1 to 15 in order, with the gap in the bottom-right corner.
The goal
This is the finished board. Everything below is about getting there without going in circles:
The solved position — 1 to 15 in reading order, gap last.
Controls
- Tap / clickMove any plaque that sits directly beside the gap. It slides into the empty socket.
- SwipeSwipe in the direction you want a plaque to travel — handy on a phone.
- Arrow keysSlide the plaque from that direction into the gap.
- New gameDeals a fresh shuffle and resets the clock.
- HapticsToggles the small vibration on each move, if your device does them.
A plaque can only ever move into the gap, and only from directly beside it — never diagonally, and never more than one at a time. That single restriction is the whole puzzle.
Every board can be solved
Only half of all possible arrangements of a 15-puzzle are actually solvable. The other half are unreachable no matter how well you play — which is the source of a great deal of historical frustration, and of at least one famous 19th-century prize that could never be won.
Fifteen checks the parity of every shuffle before dealing it and only ever hands you a solvable board. If you're stuck, it's the method — not the deal. That's a promise the game makes deliberately, so a hard board is always worth persevering with.
A method that always works
Beginners tend to solve the puzzle by wandering: pushing plaques toward roughly where they belong and hoping. That works until the last few tiles, and then it collapses, because fixing one late tile un-fixes another. The reliable approach is to solve the board in a fixed order and never disturb what's already finished.
1. Top row first, left to right
Place 1, then 2, then 3. Get 4 last. Once the top row is complete, treat it as a wall — the rest of the puzzle happens in the three rows below it, and you never move a top-row plaque again.
2. The corner trick for 4 (and 8)
The end-of-row tile is the one that traps people. Don't try to slot 4 straight into its corner. Instead, put 3 in the corner where 4 belongs, park 4 directly beneath it, and then rotate the pair into place together. The same manoeuvre finishes the second row with 7 and 8.
3. Second row, same way
Now do 5, 6, and then 7-and-8 as a pair. Two rows are now locked and you're working in a four-by-two strip.
4. The last two rows, in columns
Stop thinking in rows here. Solve the bottom two rows column by column: place 9 and 13 together, then 10 and 14 together. That leaves 11, 12, 15 and the gap in a two-by-two square, which resolves with a simple rotation. If it won't resolve, you've accidentally moved a finished tile — back up rather than forcing it.
Getting faster
- Plan the gap, not the tile. Strong players think about where the empty socket needs to travel, because the gap is the only thing that actually moves. The plaques just fill in behind it.
- Move in loops. Bringing a plaque one square closer usually takes a small circuit of the gap around it. Learning those circuits as single gestures, rather than as individual moves, is most of the speed gain.
- Don't rush the opening. The first row is cheap to solve and expensive to redo. Time lost being careful early is repaid twice over at the end.
- Fewest moves and fastest time are different games. Chasing a low move count is a slower, more deliberate way to play — and worth trying once you've got the method down.
Good to know
- Your board, move count and clock are saved on your device, so you can close the tab mid-solve and pick it up later.
- Your best time is kept locally too. Clearing your browser data clears it — there's no copy on a server.
- No account needed, and no time limit. The clock is there to race, not to punish.