Alignment subject

In CSS box alignment the alignment subject is the thing (or things) being aligned within the {{glossary("alignment container")}} by the property.

For {{cssxref("justify-self")}} and {{cssxref("align-self")}}, the alignment subject is the margin box of the box the property is set on, using the writing mode of that box. For {{cssxref("justify-content")}} and {{cssxref("align-content")}}, the writing mode of the box is also used.

The definition of the alignment subject depends on the layout mode being used.

• Block containers (including table cells)
  • : The entire content of the block as a single unit.
• Multicol containers
  • : The column boxes, with any spacing inserted between column boxes added to the relevant column gaps.
• Flex containers
  • : For {{cssxref("justify-content")}}, the flex items in each flex line. For {{cssxref("align-content")}}, the flex lines. Note, this only has an effect on multi-line flex containers.
• Grid containers
  • : The grid tracks in the appropriate axis, with any spacing inserted between tracks added to the relevant gutters. Collapsed gutters are treated as a single opportunity for space insertion.

See also

• CSS box alignment module
• Related glossary terms:
  • {{Glossary("alignment container")}}