Medium Sudoku

Easy Medium Hard Expert Master Extreme

Mistakes 0/3

Time 00:00

Score -

Select a cell, then tap a number

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Medium Sudoku - The Strategic Step Up

Medium is where Sudoku transforms from a counting exercise into genuine logical reasoning. Master these techniques and the harder levels become accessible.

How Medium Differs from Easy

Easy puzzles always have at least one cell where only a single candidate is possible - So you can always make progress with simple scanning. Medium puzzles sometimes reach a point where no cell has an obvious single. You need Hidden Singles to break the deadlock.

Feature	Easy	Medium
Given cells	40–45	32–38
Naked Singles sufficient?	Yes, always	Not always
Hidden Singles needed?	Rarely	Yes, regularly
Naked Pairs needed?	Never	Occasionally
Avg completion (regular player)	5–10 min	10–20 min

Core Techniques for Medium

Naked Single - A cell where only one candidate remains after eliminating all digits in its row, column and box. Always check for these first; they're the fastest wins.
Hidden Single - A digit that can only go in one cell within a particular row, column or box - Even if that cell itself appears to have multiple candidates. Look at each unsolved unit: for every digit 1–9, is there only one valid cell? If so, that cell is solved.
Naked Pair (basic) - Two cells in the same unit that both contain exactly the same two candidates. Those two digits are "locked in" those cells, so you can eliminate them from every other cell in the unit.

The Hidden Singles Method - Step by Step

Pick any unsolved 3×3 box and choose one digit (say, 5).
Look at every blank cell in that box. Which ones are in a row or column that already contains a 5? Cross those out mentally.
If only one blank cell remains valid for the digit 5, fill it in.
Repeat for all nine digits in all nine boxes, then do the same sweep across all rows and all columns.
Each solve creates new eliminations - Run the full sweep again after every placement.

Systematic Rescue Plan (When Stuck)

Switch to Notes mode and pencil in all candidates for every blank cell.
Look for any cell with only one pencil mark - That's your Naked Single.
For each box, check whether any digit appears as a candidate in only one cell - Hidden Single found.
Scan for two cells in a row/column/box sharing identical two-candidate pairs - Eliminate those two digits from the rest of the unit.
After each fill, erase the corresponding candidate from all peers and repeat from step 2.

Technique Usage in Medium Puzzles

Typical proportion of moves made using each technique:

Naked Singles~58%

Hidden Singles~36%

Naked Pairs~6%

Performance Benchmarks