Sudoku Strategies
Techniques tell you what to look for. Strategy tells you when and in what order. This guide gives you a routine you can use on any puzzle and a plan for moving up the difficulty levels.
A solving routine that works
Good solvers do not search randomly. They run the same loop on every puzzle:
- Scan the whole grid first. Look for digits that appear many times; they are the easiest to complete.
- Exhaust the easy moves. Place every single you can find before trying anything more complex.
- Add pencil notes only when scanning stops producing numbers.
- Eliminate with patterns. Apply pairs, pointing pairs and so on to remove candidates.
- Go back to scanning every time you place a number, starting with its row, column and box.
The patterns in step 4 are explained on our Sudoku techniques page.
Strategy by difficulty level
| Level | Main strategy | Play |
|---|---|---|
| Easy | Scan for singles. Notes are rarely needed. | Easy Sudoku |
| Medium | Hidden singles and selective pencil notes in tight boxes. | Medium Sudoku |
| Hard | Full pencil notes, pairs and pointing pairs. | Hard Sudoku |
| Expert | Box-line reduction, X-Wing and chains, with careful note upkeep. | Expert Sudoku |
Move up only when you can finish the current level without hints. Jumping too fast is the most common reason people give up on Sudoku.
Using pencil notes well
- Start with the tightest areas. Fill notes first in boxes, rows and columns that are nearly complete.
- Keep notes current. After every placement, remove that digit from the notes in its row, column and box.
- Look for short candidate lists. Cells with two candidates are where pairs and chains start.
- Do not write everything on easy puzzles. Full notes slow you down when scanning is enough.
What to do when you are stuck
- Re-scan digit by digit, 1 to 9, across the whole grid. New singles often hide where you stopped looking.
- Check your notes for a missed update.
- Look for a naked pair or pointing pair in the busiest boxes.
- Switch area. Progress in one region often unblocks another.
- As a last resort, use a hint or enter the position into the Sudoku solver, and study why the answer works.
Getting faster
- Scan in a fixed order (for example 1 to 9) so you do not repeat yourself.
- Learn the box layout so you can see at a glance that a row is blocked.
- Use the keyboard on desktop: arrow keys to move and number keys to place.
- Track progress on your stats page and play the daily Sudoku to build a streak.
Habits to avoid
- Guessing. It almost always creates a contradiction later.
- Ignoring the box. Many errors come from checking only rows and columns.
- Over-relying on hints. A hint fills one cell but teaches nothing unless you work out why it is right.
Sudoku Strategies FAQ
What is the best strategy for Sudoku?
Scan for singles first, add pencil notes when scanning stalls, then use elimination patterns such as pairs and pointing pairs. Always go back to scanning after each placement.
Should I use pencil notes in Sudoku?
Yes for medium, hard and expert puzzles, where scanning alone is not enough. Keep them updated, since stale notes cause mistakes.
How can I get better at Sudoku?
Play regularly, move up one difficulty level at a time, and learn one new technique at a time. Review puzzles you could not finish instead of just using hints.
Is it okay to guess in Sudoku?
It is better not to. A valid puzzle is solvable by logic, so a guess is a sign you are missing a technique. Use pencil notes and elimination instead.
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