An implicit grid track is a row or column that CSS Grid creates outside the explicitly declared grid. The browser adds one when an item is placed beyond the defined tracks or when extra space is needed to place all items. section 4.3
Implicit tracks matter when interpreting placement and sizing:
- Explicit tracks come from grid-template-columns or grid-template-rows; implicit tracks are generated as needed. section 4.3
- Implicit tracks still participate in the grid track sizing algorithm, including intrinsic sizing and flexible-space distribution. section 4.3
- Negative grid line numbers cannot target auto-generated implicit tracks, so placement such as grid-row: -2 / -1 can fail when grid-auto-rows creates them. section 4.2.3 section 4.5
Placing beyond the declared grid
With three explicit columns, .item { grid-column: 3 / span 5; } extends across columns 3 through 7. Columns beyond the explicit grid are implicit, while span expresses the number of tracks without manually calculating the endpoint. section 4.3 section 4.5
.item {
grid-column: 3 / span 5;
}
Inspect a placement declaration that causes the grid to extend beyond its explicitly defined columns. section 4.3
