ESTA in the US or ETA in Canada doesn't require anything extra in my experience, it's just like a flag either on or not on your passport coming through passport

ESTA in the US or ETA in Canada doesn't require anything extra in my experience, it's just like a flag either on or not on your passport coming through passport control. (I assume UK ETA is the same, but I haven't travelled in with anyone requiring one yet. My wife doesn't with a BRP which is also a euphemism for a visa if you like, and that is similarly straightforward.)