Subgrid

Introduction

When children of a grid container become grid containers themselves, they don't take track sizing from their parent.

Let's say we want our cards to have two columns with this CSS rule:

grid-template-columns: minmax(5ch, 20ch) 1fr;

Without subgrid

With subgrid

We can see that without subgrid, each card defines its' columns independently, while with subgrid, the parent defines the child's columns.

How to use subgrid

Here is the simple example of using subgrid:

Let's start with defining html structure:

<div class="grid">
    <div class="subgrid">
        <div class="grandchild"></div>
    </div>
</div>

We have to set display: grid for the main container and its' child:

.grid {
    display: grid;
}

.subgrid {
    display: grid;
}

And now it's time to define track sizing:

.grid {
    grid-template-columns: repeat(8, 1fr);
}

.subgrid {
    grid-column: 2 / -1;
    grid-template-columns: subgrid;
}

Here, track sizing of the child is inherited from the parent by setting its' own grid-template-columns to subgrid.

So, how to position the grandchild so it will occupy the cell in the third column of the grandparent?

.grandchild {
    grid-column: 2 / 3;
}

Since the child has its' own count, the second column of the child will be the third one of the parent.