Module grid_auto_columns 

Utilities for controlling the size of implicitly-created grid columns.

Class	Properties
auto-cols-auto	grid-auto-columns: auto;
auto-cols-min	grid-auto-columns: min-content;
auto-cols-max	grid-auto-columns: max-content;
auto-cols-fr	grid-auto-columns: minmax(0, 1fr);

Arbitrary values

Any property is allowed as arbitrary value. For example, auto-cols-[10%_33.3%].

Tailwind reference