Technique 2 of 8 · Start here
Find the cells a satisfied number makes safe
The guide and all minesweeper techniques
Minesweeper techniques
- 1Finding certain minesStart here
- 2Finding safe cellsStart here
- 3Flagging and chordingCore technique
- 4Comparing neighbouring numbersShared cells
- 5Subtracting known minesSimplifying clues
- 6The 1–2–1 patternRecognising patterns
- 7The 1–2–2–1 patternRecognising patterns
- 8Using the remaining mine countFinishing a board
Once a number has all its mines accounted for, every other cell it touches is safe. You can use this even when those safe cells touch other, unresolved numbers.
The flags in these examples have already been proved. If one of your own flags was a guess, counting it as a fact would make the reasoning unreliable.
Example 1: The mine is already accounted for
Step 1 of 3
The flag is a mine proved earlier. Read the top 1 and count its covered neighbours.
The top 1 touches the proved flag and the covered cell above it. The flag supplies its one mine, so the covered cell cannot contain another.
The bottom 1 gives the same conclusion for the lower covered cell. Both can be chosen safely. The ticks show that deduction without inventing numbers for cells we have not opened.
Work inside the solid frame. Every possible mine neighbour of these clues is inside it. Cells beyond the frame are background, not revealed zeros or extra clues.
Flags are proved mines. A tick marks a cell proved safe; its number is not shown.
Blue-ringed numbers are the clues to compare. Shading marks the cells being discussed.
Try it yourself
Try the reasoning yourself. Choose an answer to see the explanation.
The middle flag was proved earlier. Find every other covered cell that these clues make safe.
Practice only: no clock, saved game or hint charge.
Task 1 of 1: Choose both safe cells.
Choose a cell on the board.
Work inside the solid frame. Every possible mine neighbour of these clues is inside it. Cells beyond the frame are background, not revealed zeros or extra clues.
Practice close-up: rows 1–4, columns 1–4.
Flags are proved mines. A tick marks a cell proved safe; its number is not shown.
How to spot it faster
- Revisit numbers beside each new flag; several can become satisfied at once.
- Separate what you have proved from what you merely suspect.
- A blank cell means zero adjacent mines. Its neighbours are safe too.
Common mistakes
Trusting an unproved flag
A flag is your annotation. The board does not certify it. If a deduction leads to a contradiction, check the flags that deduction relied on.
Expecting a safe cell to be blank
Safe means no mine in that cell. It may still show a number because there are mines beside it.
Questions
Further reading
Try it
After each certain flag in solo play, check the surrounding numbers. Before opening a cell, identify the satisfied clue that makes it safe.
Play solo Minesweeper