Title says it all. Headed to Heathrow from Logan in about a week. Have a nice valid USA passport. Will be staying for a few days doing touristy things (Watching Ireland play Wales in a Six Nations Rugby match in Cardiff).
I just went through the same process @Ruken describes. Painless except for the GBP10 ~= USD13 fee at the end.
Your ETA is good for an unlimited number of visits to the UK over the next IIRC 3 years. That doesn’t mean you could go there and stay all 3 years. Just that you only need to get the ETA once for any all travel into the UK during that time.
You didn’t ask, but the EU is starting a very similar thing called the ETIAS that was supposed to go into effect on Jan 1 2025 but is presently delayed until May 1 2025. The UK ETA is similar and it did go into effect on time on Jan 1 2025.
If you haven’t already, I wasn’t able to scan my passport’s chip/RFID/whatit with my phone. Rather than trying three times like I did, you can just enter the info.
They really want you to use their app rather than the website.