Scanning
The basic search method: follow a digit's rows and columns to see which cells it can still occupy.
What it is
Scanning means taking one digit and tracing the lines it already occupies. Every row and column containing that digit is closed to it everywhere else, so those lines slice through neighbouring boxes and eliminate cells. What remains are the digit's possible homes — and often there is only one. Scanning is not a pattern but a habit, and it is how nearly all solving without pencil marks is done.
How to spot it
Choose a digit that already appears several times, since more copies mean more blocking lines. Take one box at a time and mentally draw lines from every copy of the digit in the surrounding rows and columns. Cells the lines pass through are ruled out. If a box has one free cell left for that digit, place it.
Worked example
Step through the reasoning below. Each step adds one layer: first the position, then the pattern, then the candidates involved, and finally what can be eliminated.
Step 1 of 3: The starting position
- Pattern cells
- 3/3
- Digits
- 8
- Eliminations
- —
Press a marked square to point it out on the board above.
Why it matters
Scanning finds most placements in easy and medium puzzles without writing a single note. It is fast, needs no bookkeeping, and it trains the visual sense that later techniques build on.
Frequently asked questions
Do I need to write anything down when scanning?
No. Scanning is deliberately a mental technique. Notes become useful when scanning stops producing placements, typically on hard puzzles.
Which digit should I scan first?
The one that appears most often. Six or seven copies of a digit create many blocking lines, so the remaining cells are heavily constrained.
Put it to use
Where you will meet it
This pattern is the backbone of easy grids. Start one and you will use it within a few moves.
Play EasyStuck on a grid of your own?
Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.
Open the solverPrefer paper? Ready-made Easy sets as a PDF.Print puzzles
Finished reading? Mark it done and the learning path remembers where you got to.