Sudoku Tips & Strategy
Getting better at Sudoku isn’t about speed or guessing — it’s about learning the solving techniques and using them in the right order. Here is the strategy that cracks every difficulty, from your first Easy grid to Expert.
Start every puzzle the same way
Before anything clever, sweep the whole grid for the two kinds of single: a naked single (a cell only one digit can fill) and a hidden single (a digit only one cell in a house can take). Easy puzzles are often solved on singles alone. Place every single you can find, then look again — each placement usually creates the next.
When singles run dry, pencil in candidates: the small digits each empty cell could still hold. Almost every technique beyond singles is read off these pencil marks, so keep them accurate.
The solving ladder
Learn — and apply — these techniques in order, cheapest first. Each links to a free, illustrated guide with a worked example:
- Naked singles — a cell with only one candidate left — the first thing to scan for.
- Hidden singles — a digit with only one home in a row, column or box.
- Naked pairs — two cells sharing the same two candidates, clearing them from the unit.
- Hidden pairs — two digits confined to the same two cells, hidden among others.
- Pointing pairs — a candidate locked to one line inside a box, pointing along that line.
- Box/line reduction — a candidate a line confines to one box, clearing the rest of the box.
- Naked triples — three cells that between them use only three candidates.
- Hidden triples — three digits confined to the same three cells.
- X-Wing — a rectangle on one digit that eliminates across two lines.
- Skyscraper — two two-cell lines of a digit sharing a base, eliminating at the roofs.
- Two-string kite — a row link and a column link of a digit that meet in a box.
- XY-Wing — a pivot and two wings that force a digit out of a shared cell.
- XYZ-Wing — a three-candidate pivot with two wings, all sharing one digit.
- Swordfish — the three-line version of an X-Wing on a single digit.
The golden rule: always exhaust the earlier rungs before reaching for a later one. A clean, cheapest-first solve almost never gets stuck.
Top tips
- Hunt the most-constrained cells. Cells and houses that are nearly full give up singles and pairs first — start where the grid is busiest.
- Switch digit when stuck. Pick one number and ask where it can still go in each row, column and box; a hidden single or a fish often appears.
- Never guess. Every proper Sudoku is solvable by logic alone. If you feel like guessing, there is a deduction you have missed — slow down and re-scan.
- Keep pencil marks current. The instant you place a digit, remove it from its peers’ candidates. A stale mark leads to a wrong elimination and a broken grid.
Frequently asked questions
How do I get better at Sudoku?
Learn the solving techniques in order and use them in that order every puzzle: scan for singles first, then pairs and locked candidates, then the harder patterns like the X-Wing. Each technique you add lets you finish harder grids without ever guessing.
What is the best strategy for Sudoku?
Always exhaust the cheapest moves first. Fill every naked and hidden single, then look for naked/hidden pairs and pointing pairs to trim candidates, and only reach for fish and wings when the simpler moves stall. Working cheapest-first keeps the grid clean and avoids guessing.
Do I have to guess in Sudoku?
No. Every proper Sudoku has exactly one solution reachable by pure logic, so if you are guessing you have missed a deduction. When you are stuck, switch digit — pick a number and ask where it can still go in each row, column and box; that often reveals a hidden single or a pattern.
Should I write in candidates (pencil marks)?
For easy puzzles you can often solve on singles alone, but from Medium upward pencil marks are essential — most techniques (pairs, triples, X-Wings) are read off the candidates, not the given digits. Keep them accurate: an out-of-date pencil mark leads to wrong eliminations.