All Octicons
square-fill
Octicon sizes navigation
React
import {SquareFillIcon} from '@primer/octicons-react' <SquareFillIcon size={16} />
Rails
<%= render(Primer::Beta::Octicon.new(:"square-fill", size: :small)) %>
Jekyll
{% octicon square-fill height:16 %}
Figma
This icon is called square-fill
in Primer's Octicons library.