smooth transitions between pages that regular users would not think of as separate pages

Honestly expect this to be good enough without JavaScript, switching between pages on a site are not jarring if it is well set up, but i want to test if CSS transitions do their thing while the next page is loading or if JS will be needed for that.

This looks like one of the lightest and nicest JavaScript libraries for this:

But here are a bunch more (not all reliant on JQuery i trust) -