The ::view-transition CSS pseudo-element represents the root of the view transitions overlay, which contains all view transition snapshot groups and sits over the top of all other page content.
During a view transition, ::view-transition is included in the associated pseudo-element tree as explained in The view transition pseudo-element tree. It is the top-level node of this tree, and has one or more ::view-transition-groups as children.
::view-transition is given the following default styling in the UA stylesheet:
html::view-transition {
position: fixed;
inset: 0;
}
All ::view-transition-group pseudo-elements are positioned relative to the view transition root.