Upvote:8
From the ESTA FAQ (my emphasis):
Can I apply for an ESTA without having confirmed travel plans?
Yes. Specific travel plans are not mandatory at the time of application, but you will need a U.S. point of contact.
Although specific travel plans are not required, the address where you will be staying in the United States is recommended to complete the application. If multiple locations are planned, you only need to enter the first address. If a complete address is not known, you can enter the name of the hotel or location you will visit.
If you are in transit, please select 'yes' to the 'Is your travel to the U.S. occurring in transit to another country?' question in the Travel Information section.