Medium sudoku puzzles
Medium sudoku is where the puzzle starts to push back. There are fewer starting digits, so simple scanning runs out and pencil notes start to earn their place. You will use hidden singles and pointing pairs, but you will never need to guess.
The boards are unlimited and generated fresh each time. Once medium feels comfortable, try hard sudoku for pairs, triples and X-Wings.
What makes a sudoku medium?
Medium puzzles cannot be finished by scanning alone. At some point every cell has two or more possible digits, and you need pencil marks and a few simple techniques to find the next certain move.
The techniques you need
- Naked singles. When you list the candidates of a cell and only one digit is possible, write it in.
- Hidden singles. A digit that can only go in one cell of a row, column or box belongs there, even if that cell has other candidates.
- Pointing pairs. If, inside one box, a digit’s candidates all lie in the same row, that digit cannot appear anywhere else in that row outside the box. Remove it from those cells.
- Box-line reduction. The reverse: if in a row a digit can only go in cells within one box, remove it from the rest of that box.
A good routine
Fill in everything you can by scanning first. Then add pencil marks to the busiest boxes, those with the fewest empty cells, and look for singles. After every digit you place, update the pencil marks in its row, column and box; stale notes are the most common cause of mistakes.
How to play here
Tap a cell and type a digit, or use the number pad on a phone. For pencil marks, right-click a cell on a computer, or switch on Mark mode on a phone and tap the cell before entering digits. When medium puzzles feel comfortable, try hard sudoku.
How to play Medium Sudoku
- Fill every empty cell with a digit from 1 to 9.
- Each row, each column and each 3×3 box must contain every digit exactly once.
- The starting digits are fixed. Only the empty cells are yours to fill.
- Medium boards can be solved by logic alone, but some steps need notes of the possible digits.
Medium Sudoku tips
Start with pencil marks in the busiest boxes
Note the possible digits in boxes that are already half full. Small lists are easier to read, and the first single candidates usually appear there.
Hunt hidden singles
A digit can have only one possible cell in a row, column or box even when that cell has other candidates. Look for the digit, not the cell.
Use pointing pairs
If a digit's candidates inside one box all sit in the same row, that digit can't appear anywhere else in that row. Cross it out of the rest of the row.
Frequently asked questions
What is the difference between easy and medium sudoku?
Easy boards fall to simple scanning. Medium boards have fewer starting digits and need candidate notes, hidden singles and pointing pairs.
Do I need to guess on medium sudoku?
No. Every medium puzzle here has one solution that can be reached by logic. If you feel you must guess, check your notes for a missed candidate.
How do I get faster at medium sudoku?
Keep your notes complete and up to date. Most slow solves come from a missing candidate that hides the next move.
