Minesweeper rules
A number tells you how many mines touch that field. Everything else in the game follows from counting.
The rules in one sentence
The field hides a known number of mines; uncover every square that is not a mine and the field is cleared. Uncover a single mine and the game is over.
What a number means
When you uncover a square that is not a mine, it shows how many of its eight neighbours are mines — including diagonals. A blank square means zero neighbouring mines, which is why blank areas open up in one move: there is nothing around them that could be dangerous.
That single sentence is the whole game. Everything else is a consequence of it:
- A 1 touching exactly one covered square: that square is a mine.
- A 2 with two covered squares left: both are mines.
- A number with all its mines already flagged: every other neighbour is safe.
Flags
A flag is a note to yourself: I have worked out that this is a mine. It does nothing mechanically except two useful things — a flagged square cannot be uncovered by accident, and flags are what make chording possible.
The mine counter above the field shows the number of mines minus the number of flags you have placed. It can go negative, and that is deliberate: it means you have flagged more squares than there are mines, so one of them is wrong.
Chording
Click a number that already has as many flags around it as its value, and every remaining covered neighbour opens at once. This is the fastest legal move in minesweeper and the reason experienced players flag before they open.
The catch is fair: if one of those flags is wrong, chording uncovers a mine and the game ends. Chording trades speed for trust in your own flags.
What counts as a mistake here
Exactly one thing: uncovering a mine. Not a wrong flag, not a slow field, not an abandoned game. One mine ends the game — and that is defensible precisely because of the next point.
Why you never have to guess
Every field on this site is generated and then verified by a solver that plays it using only three rules: the number rule described above, subtraction between overlapping numbers, and the global mine counter. Any field the solver cannot finish is discarded before it ever reaches a player.
Classic minesweeper does not work this way, and in the last corner of a classic expert board you sometimes genuinely have to flip a coin. A timed global leaderboard cannot be built on coin flips, so here it is a hard rule: if you are stuck, the information exists.
The four things beginners get wrong
- Opening squares one at a time. Flag first, then chord — the same field takes a third of the time.
- Reading one number at a time. Most positions are resolved by two numbers together, not by either one alone.
- Ignoring the counter. At the end of a field it often settles a whole region no local rule can.
- Guessing when stuck. On this site that is always the wrong move: the answer is on the board, usually two squares from where you are looking.
Ready? Start on easy, or read the strategy page for the patterns that solve the hard fields.