Flutter crossAxisAlignment vs mainAxisAlignment

For Row:

mainAxisAlignment = Horizontal Axis
crossAxisAlignment = Vertical Axis

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For Column:

mainAxisAlignment = Vertical Axis
crossAxisAlignment = Horizontal Axis

Image source

Row/Column are associated to an axis:

• Horizontal for Row
• Vertical for Column

mainAxisAlignment is how items are aligned on that axis. crossAxisAlignment is how items are aligned on the other axis.

When you use a Row, its children are laid out in a row, which is horizontally. So a Row's main axis is horizontal. Using mainAxisAlignment in a Row lets you align the row's children horizontally (e.g. left, right). The cross axis to a Row's main axis is vertical. So using crossAxisAlignment in a Row lets you define, how its children are aligned vertically.

In a Column, it's the opposite. The children of a column are laid out vertically, from top to bottom (per default). So its main axis is vertical. This means, using mainAxisAlignment in a Column aligns its children vertically (e.g. top, bottom) and crossAxisAlignment defines how the children are aligned horizontally in that Column.

This two pictures are clear to show the meaning of MainAxisAlignment and CrossAxisAlignment.

(Pictures are from Network)