The word "technique" makes sudoku sound intimidating. It isn't. Every technique below is just a slightly smarter way of asking the same question: where can this number go? Learn these four, in this order, and you'll finish the vast majority of easy and medium puzzles without ever guessing.
Start easy, always
Before any technique matters, one rule matters more: start on easy puzzles. Easy grids are where techniques reveal themselves clearly. Hard grids hide the same techniques under noise — which is exactly why beginners who start hard conclude they're "bad at sudoku". You're not. You just skipped the lessons.
There is never any arithmetic in sudoku. The nine digits could be nine different fruit. It's pattern logic wearing a number costume.
1 · Scanning
Scanning is the first thing you'll do on every puzzle and the last thing you'll stop relying on. Pick a digit — say, the one that already appears most often — and look at where its copies live. Each copy blocks its entire row, its entire column, and its 3×3 box. Follow those blocks and you'll often find a row or box with only one square left where that digit can go.
2 · Crosshatching
Crosshatching is scanning aimed at a single box. Take one 3×3 box and one digit, then mentally draw lines in from every row and column that already contains that digit. Those lines cross out squares in your box. If only one square survives, that's where the digit goes.
It sounds mechanical because it is mechanical — and that's the point. On easy puzzles, patient crosshatching alone will solve box after box with zero cleverness required.
3 · Pencil marks
Once scanning stops handing you free squares, switch on pencil marks. In every empty cell, write tiny candidate digits — the numbers that could still legally go there. Every sudoku app has a notes button for this, and on paper it's the small numbers in the corner.
- This is not cheating. It is literally how expert solvers and championship players work.
- As you place real digits, erase them from the candidate lists in the same row, column and box.
- Watch what happens to those lists as they shrink — which brings us to the payoff.
4 · Naked singles
A naked single is a cell whose pencil marks have collapsed to exactly one candidate. There's nothing left to decide — that digit was hiding in plain sight, and you can write it in. The satisfying part is the cascade: filling one naked single removes a candidate elsewhere, which often creates the next naked single, and so on.
After placing any digit, glance at its row, column and box for a cell that just dropped to one candidate. Chasing that chain is what makes a puzzle "click".
Putting it in order
On any new easy or medium puzzle, run the techniques in this sequence:
- Scan the fullest digits for obvious placements.
- Crosshatch box by box to squeeze out a few more.
- Pencil-mark the remaining empty cells once easy wins dry up.
- Hunt naked singles and ride the cascade to the end.
That's the whole beginner toolkit. When these start to feel automatic, the next tricks — naked pairs, hidden pairs, X-wings — are waiting in the sudoku hub. But honestly? Not yet. Finish a hundred easy grids first.