UK ETA – for anyone transiting through the UK
Effective January 8, 2025, all U.S. citizens transiting the UK or traveling to the UK for tourism, family visits, business meetings, conference, or short-term study for 6 months or less will require an Electronic Travel Authorization (ETA) prior to travel.
Here is a link to information on the ETA. The cost is 10 euros per person and can be paid by credit card. Note that processing can take up to three days or more.
The easiest way to apply is to use the phone app UK ETA. To use the app, you will need a photo of your passport and a photo of yourself. If you are applying on behalf of someone else, you can apply online rather than using the phone app. Here is a link with information for the application process.