How to play the 15 puzzle

1

Pick a board size

Start with 3×3 to learn the ropes, then graduate to the classic 4×4 (the real "15 puzzle") or the brutal 5×5.

2

Slide tiles into the gap

Tap any tile next to the empty square to slide it in — or use your arrow keys. Only tiles beside the gap can move.

3

Order them 1 → N

Finish when the tiles read 1, 2, 3… left-to-right, top-to-bottom, with the empty square in the bottom-right corner. Fewest moves wins.

Tips to solve it faster

  • Work row by row. Finish the entire top row before touching the second. Lock each completed row mentally and never disturb it.
  • Learn the pair trick. The last two tiles of a row are the hard part — manoeuvre them into place together as a pair instead of one at a time.
  • Don't chase single tiles. Moving one tile into place usually wrecks two others. Plan 3–4 moves ahead and think in cycles.
  • Keep the blank useful. The empty square is your only tool — park it near the tiles you're placing, not in a finished row.
  • Undo with Reset. Made a mess of a solved row? Hit Reset to restart the same shuffle and try a cleaner route.
Why some puzzles are impossible: a randomly shuffled sliding puzzle is unsolvable about half the time (it's a parity thing mathematicians worked out in the 1870s). Every board on this page is built by scrambling from the solved position with legal moves — so a solution always exists. If you ever feel stuck, it means the path is tricky, never impossible.

Which board size should you play?

BoardTilesDifficultyGood for
3×38⭐ EasyKids, warm-ups, learning the row-by-row method
4×415⭐⭐⭐ ClassicThe original 1870s puzzle — a proper brain workout
5×524⭐⭐⭐⭐⭐ ExpertPatient strategists; expect 300+ moves at first

Frequently asked questions

How do you play the 15 puzzle?

Slide numbered tiles into the empty space until they read 1, 2, 3… in order, with the gap last. Tap a tile next to the gap, or use arrow keys.

Is every shuffle on this page solvable?

Yes. Boards are generated by random legal moves from the solved position, which guarantees solvability. Pure random shuffles are unsolvable ~50% of the time — we never use those.

What is a good move count?

On 4×4, finishing under 150 moves is solid and under 100 is strong. The hardest 4×4 positions need exactly 80 optimal moves.

Can I play on my phone?

Yes — tap the tiles. The board resizes to any screen and needs no app.

Is it good for your brain?

It trains planning, pattern recognition and working memory. A few relaxed rounds are a great daily brain break.

🔗 See also

  • Tower of Hanoi — another classic disk puzzle
  • Sudoku — number logic, pen-and-paper style
  • 2048 — sliding tiles, merge edition