How Medium Sudoku changes the puzzle
Medium puzzles leave fewer immediate placements than Easy boards. A basic scan still matters, but the next move is more often uncovered by comparing candidate possibilities across a row, column, and box.
Candidate Notes
Candidate notes make uncertainty visible. Fill them carefully, then revisit the unit after every confirmed number. A useful note is one you are prepared to update.
Hidden singles
A cell may have several candidates while one digit can occur in only one place in a unit. That is a hidden single: scan digit by digit when a row does not offer an obvious empty cell.
Scan with intention
Instead of racing around the grid, choose a box or a digit and work through it completely. That slower rhythm makes restrictions easier to notice.
Introduction to pairs
When two cells in a unit are restricted to the same two candidates, those candidates are reserved there. Spotting this basic pair can free up a later single.
When to move to Hard
Try Hard Sudoku once candidate notes and hidden singles feel familiar. You do not need to solve every Medium board instantly; consistent, explainable moves are the better signal.