Ah, very interesting example thanks. We're back to definitions of UI and UX and the overlap between the two :-) That example you gave, whilst obviously literal

Ah, very interesting example thanks. We're back to definitions of UI and UX and the overlap between the two :-) That example you gave, whilst obviously literally an update of the UI, I would punt as being more a UX change, actually. The reason is that the point of it is what you say - to reduce friction of the checkout flow by not forcing you to wait until you do that to change your address, but letting you do it ahead of time so that next time you check out, you're just a couple of clicks away from hitting the 'pay' button - as opposed to leaving functionality the same and just making things look nicer. Obviously this change is physically implemented as a UI change, but my question would be did the nav bar's design, position on the screen, etc, change? No - it was a flow change implemented within the existing UI design metaphors. What I'm more alluding to with UI changes is changing those designs and metaphors, with the hope of making the UX 'nicer' as a result. This only works if nicer UI is nicer UX. In Amazon's case that's not true, so they stick with the same server-rendered pages, buttons, navbar, form fields, etc etc that they've had forever. They make flow changes within that UI though, of course, to facilitate better UX.