🔢 Number Slide

The classic number slide puzzle, free online

Number Slide is a free version of the classic sliding tile puzzle, sometimes called the number slider, the fifteen puzzle or the 15 puzzle. Numbered tiles sit in a square grid with one empty space. You slide the tiles into the gap, one at a time, until they're back in order. It's easy to learn and surprisingly hard to do quickly. There is nothing to download, and it works with a mouse, a keyboard or a touch screen.

What is the fifteen puzzle?

The fifteen puzzle uses a 4 x 4 grid: fifteen tiles and one empty space. It became a huge craze in the 1880s, in the United States and in Europe, with people playing it at work, on trains and at home. Since then it has become one of the best-known puzzles in the world, and it's still used by computer scientists to test search methods. Exactly half of all possible arrangements of the tiles can't be solved, which caused quite a stir at the time. In this game the tiles are always shuffled using real moves, so every board can be solved.

How to solve a 4 x 4 grid

Don't try to move all the numbers at once. Solve the puzzle in layers. First get 1 and 2 into place along the top row. The last two tiles in a row are the tricky part, so bring 3 to the far corner and 4 directly below it, then slide them both into place together. Do the same for the second row. Now you've got a 2 x 4 space left, so treat it column by column: place 9 and 13 together, then 10 and 14. The last three tiles just rotate around the gap. Once you've learned this method, the same idea will solve the 5 x 5 and 6 x 6 too.

Four sizes, from easy to expert

The 3 x 3 grid, with 8 tiles, is perfect for beginners and young players. The 4 x 4 grid is the original challenge. The 5 x 5 grid, with 24 tiles, is a real test of patience, and the 6 x 6 grid, with 35, is for experts. For each one, finish under the target number of moves for 3 stars, or under twice the target for 2 stars. Any solve earns 1 star. Your best score for each size is saved on your device.

Picture mode

Prefer a picture? In picture mode, the tiles make up a scene: a house on a hill, a rocket in space, a fish at sea or a friendly cat. There are no numbers to guide you, so you have to work out where each piece belongs by its shape and colour. It's great for younger children who don't want to think about numbers, and it adds an extra challenge for everybody else. Press the eye button at any time to see the finished picture.

Why sliding puzzles are good for your brain

Sliding puzzles build planning and spatial thinking, because each move depends on the one after it. You have to think ahead, and sometimes you must move tiles away from where they belong to get them home later on. That idea, going backward to go forward, is useful far beyond puzzles.

Tips for fewer moves

Once you can solve the puzzle, the real game begins: doing it in fewer moves. Before you touch anything, look at where the next tile is and plan the shortest route to bring the gap around to it. Try not to chase a tile back and forth, because each slide counts. Use the gap like a tool: it should arrive on the far side of the tile you want to move, so that the tile slides toward home. Avoid disturbing tiles you have already placed, unless you are doing the two-tile trick at the end of a row. On a keyboard the arrow keys are quickest, because your hand never has to leave them. Good players often solve a 4 x 4 in well under 90 moves, and the world's best speedsolvers finish it in a few seconds, so there's always room to improve.

Number Slide for kids and classrooms

Sliding puzzles are a simple, quiet activity for children from about six. The 3 x 3 picture mode is a gentle way in, since there's nothing to read and the picture tells you when you're getting close. Number mode reinforces counting and number order, and the green tiles give instant feedback when a number reaches its place. In class, try a whole-group challenge on a shared screen, with children suggesting the next move, and talk about why a move that seems backward can be the right one. It also makes a nice calm-down game for the end of a busy lesson, because there's no timer pressure unless you want it.

More logic puzzles

If you like sliding things, try Unblock Me, Gridlock or Rush Hour Bus. For number logic, try Number Nine, our sudoku-style puzzle, or Puzzle Numbers. Every puzzle is on the Brain Games page.

Free and safe

Number Slide is free to play, with no download, no sign-up and nothing to buy. There is no chat, and your scores are saved only on your own device. See the Parents & Safety page for more.

Frequently asked questions