What a number tells you
An open cell shows how many mines touch it, counting all eight cells around it, diagonals included. A cell in a corner has only 3 neighbours and a cell on an edge has 5, so numbers there are easier to use. A blank open cell has no mines around it, which is why the game opens its neighbours for you.
Read a number backwards. Look at the covered cells around it and ask how many of them can be mines. When the number is the same as the count of covered neighbours, every one of them is a mine. When the mines you already know about use the number up, every other covered neighbour is safe. Almost every pattern below is one of those two ideas.
In the diagrams, M marks a covered cell that must be a mine and S one that must be safe. Each board is a whole board, so its edges are real edges and every number has all its neighbours in view.
A number with only one place to go
The simplest case: a number whose covered neighbours match the number. Here every 1 beside the top-left corner touches exactly one covered cell, so that cell is a mine. The same is true at the bottom right.
The same rule works for bigger numbers. Below, the 2 in the bottom-left corner touches only two covered cells, so both are mines. The middle number is also a 2, and it already has those two mines, so the third covered cell next to it is safe.
The 1-2-1 and 1-2-2-1 patterns
Along a flat edge these two patterns come up all the time. In 1-2-1, the covered cells under the two 1s are mines and the one under the 2 is safe. In 1-2-2-1, the two cells under the 2s are mines and the cells under the 1s are safe.
One warning. These boards are complete, so the 1s have no other covered neighbours. On a larger board, check that the 1s at the ends do not touch extra covered cells before you trust the pattern. If they do, count again.
Flags and chording in our game
A flag is a note to yourself: you are sure this cell is a mine. It also protects the cell from an accidental click. You do not need to flag every mine to win, because the game is won when every safe cell is open, but flags are what make chording possible.
| Device | Open a cell | Flag a cell | Chord on a number |
|---|---|---|---|
| Mouse | Left-click | Right-click | Left-click the number |
| Touch | Tap | Long-press (about 0.4 seconds), or switch on Flag mode and tap | Tap the number |
| Keyboard | Arrow keys to move, then Space or Enter | F | Space or Enter on the number |
Chording opens all the other covered neighbours of a number in one go, but only when the number of flags around it is exactly the same as the number. It does nothing if there are fewer or more flags. In Flag mode, tapping an open number still chords, so you do not have to switch modes.
Chording trusts your flags. Take the centre 2 on the 3 by 3 board below. With flags on the two top corners, which are the real mines, one chord opens the other six cells. With one flag misplaced, the same chord opens a mine and the run ends.
The habit that follows: flag only what the numbers prove, and look at the flags around a number before you chord on it. Our boards can always be solved by logic, so a guess is never needed. If you are stuck, look again along the edge of the open area.
Practise in the game
Open Minesweeper on Beginner (9 by 9, 10 mines) and look for these shapes along the edges first. Your first click is always safe, and your best time is saved for each board size. If you like deduction puzzles, Sudoku trains the same habit of ruling cells out.