When the spec talks about the transition root pseudo-element, sometimes abbreviated to “transition root”, it means the ::view-transition pseudo element.

transition root pseudo-element
a ::view-transition. Initially a new ::view-transition

In #9908 we resolved on adding a transitionRoot property to a ViewTransition instance that reflects the element hosting the VT.

There is a mismatch between the two uses of “transition root” here. In one case it’s the ::view-transition pseudo-element and in the other case it’s the element that hosts the VT + ::view-transition pseudo-element tree.

I think we should rename one of both, to prevent confusion. I am leaning towards renaming the “transition root pseudo element” because in the Scoped View Transitions explainer, the term “scoped transition root” is also used to target the element hosting the VT.

In my talks I have often referred to the ::view-transition pseudo-element as the “View Transition overlay”. Perhaps we should use that term for it?