Mini Sudoku uses a 6x6 board with digits 1 to 6. Instead of nine 3x3 boxes, the board is split into 2x3 regions, so the shape is smaller but the core rule is still instantly familiar.
The shorter format makes it ideal when you want a proper puzzle without committing to a full 9x9 solve. It is quick, but it still punishes careless placements.
Each row, column, and 2x3 region must contain 1 through 6 exactly once. Because there are fewer digits, eliminations happen faster and notes are easier to manage.
Mini is especially good for learning scanning. You can see the whole puzzle at once, so cause and effect becomes clearer than on a larger grid.
Mini Sudoku is a great warm-up for Classic, Killer, and Jigsaw. It trains the same habits: avoid repeats, check regions carefully, and find forced moves before guessing.