Minesweeper Techniques: Three Rules, No Guessing
Three rules solve every daily Minesweeper board. They are the rules of the solver that tests the boards, so nothing else is ever needed.
Last updated: September 29, 2026
Before you start: what a number still needs
For every open number, two values matter: how many mines it still needs, and which closed cells around it are still undecided.
The number still needs its value minus the flags around it. A 3 with one flag next to it needs 2 more mines. The undecided cells are its closed neighbours without a flag.
All three rules compare these two values.
Rule 1: counting around one number
- If a number needs as many mines as it has undecided cells, all of them are mines. Flag them.
- If a number needs no more mines, all its undecided cells are safe. Open them.
Example: an open 2 has three closed neighbours, and one of them carries a flag. It needs 1 more mine and has 2 undecided cells, so nothing is certain. A 1 next to it touches the same flag. It needs 0 more mines, so its other closed neighbours are safe.
Example: an open 3 in a corner of the opened area has exactly three closed neighbours and no flag. All three are mines.
This rule alone opens a large part of every board. Apply it after every move, because each new flag and each new number changes the count of its neighbours.
Rule 2: comparing two numbers
Take two numbers whose undecided cells overlap, such that all undecided cells of the first also belong to the second. The second number then has some extra cells. The mines in the extra cells are the difference of what the two numbers still need.
- If the difference is 0, the extra cells are safe.
- If the difference equals the number of extra cells, the extra cells are all mines.
Example with a safe cell: two open numbers lie side by side along a closed row. The left number is a 1 and touches the closed cells a and b. The right number is a 1 and touches a, b and c. The mine of the left number is in a or b, and this mine is also the one mine of the right number. So c is safe.
| First number | Second number | Extra cells | Result |
|---|---|---|---|
| 1, touches a and b | 1, touches a, b and c | c | 1 − 1 = 0 mines: c is safe |
| 1, touches a and b | 2, touches a, b and c | c | 2 − 1 = 1 mine: c is a mine |
| 1, touches a and b | 3, touches a, b, c and d | c and d | 3 − 1 = 2 mines: c and d are mines |
| 1, touches a and b | 2, touches a, b, c and d | c and d | 2 − 1 = 1 mine in two cells: nothing certain |
Where to look: at the first number of a row of numbers along a straight border of closed cells or along the edge of the board. It touches two closed cells, its neighbour touches the same two and a third.
Rule 3: counting the remaining mines
The board has 20 mines. The line above the tools shows how many flags are placed. Treat the whole board like one large number: it needs 20 minus the flags, and its undecided cells are all closed cells without a flag.
- If no mine is left, every closed cell without a flag is safe.
- If as many mines are left as there are closed cells without a flag, all of them are mines.
Example: 20 flags are placed and you are sure of each. Three closed cells in a corner are touched only by flags and by each other, so no number tells you anything about them. Since no mine is left, they are safe.
This rule is needed rarely: in the puzzles published so far, on fewer than 3 boards in 100. But when it is needed, the first two rules cannot replace it. It requires that all your flags are correct.
A worked sequence
- Open the start cell. An area opens, bordered by numbers.
- Walk along the border and look for numbers with as many closed neighbours as they need mines. Flag these cells. (Rule 1)
- Walk along the border again. Every number whose flags are complete gives safe cells. Open them, or press the number to open them together. (Rule 1)
- When rule 1 gives nothing, compare neighbouring numbers along straight parts of the border. (Rule 2)
- Near the end, compare the flags with the 20 mines. (Rule 3)
Common mistakes
- Taking the difference of two numbers that only share some cells. Rule 2 needs all undecided cells of one number to belong to the other; for numbers that only overlap, see the patterns guide.
- Forgetting flags in the count. A number that touches a flag needs one fewer mine.
- Using rule 3 with a doubtful flag. One wrong flag makes the count of remaining mines wrong.
- Opening a cell because the alternative looks unlikely. On the daily board a certain move exists at every moment; keep looking.
- Working in one corner for too long. If an area gives nothing, another part of the border usually does, and its result comes back to help.
Frequently asked questions
- Are three rules really enough?
- For the daily boards, yes. A board is published only if a solver that knows these three rules and nothing else opens every safe cell from the start cell.
- Do classic Minesweeper boards need more?
- Boards with random mines can need reasoning over three or more numbers at once, and some cannot be solved without a guess. Such boards are not used here.
- Should I flag every mine I find?
- It helps. Flags make the counting of rule 1 and rule 3 visible, and they make it possible to open around a number with one press.
- What are the 1-1 and 1-2 patterns that players talk about?
- They are the first two rows of the table in rule 2, seen along a straight border of closed cells: next to a 1 that touches two cells, a 1 makes the third cell safe and a 2 makes it a mine. The patterns guide shows these and the 1-2-1, 1-2-2-1 and corner patterns with diagrams and practice boards.
- I am stuck. Does the board need a guess after all?
- No. Check first that every flag is justified by a number. Then go through the border once with rule 1 and once with rule 2, and finally count the remaining mines.