Medium Sudoku — Play Free Online

Medium is where Sudoku starts asking questions instead of answering them. With fewer givens on the board, scanning alone no longer clears the grid — somewhere in the middle of the solve the direct moves dry up, and you'll need your first real elimination technique to break through.

That technique is usually locked candidates: when a digit's only spots in a box line up along a single row or column, it can be eliminated from the rest of that line — often exactly the crack the puzzle was hiding. This is also the tier where pencil marks begin to pay for the time they take, and where pointing pairs become a reliable tool.

A good habit at this tier: play the first half of the grid without notes, and switch them on the moment direct scanning stalls. You'll finish some grids without ever needing them — and on the ones where you do, you'll know precisely which technique earned the breakthrough. That awareness is what turns puzzle-solving into skill-building.