It is not possible to extend ESTA. However, ESTA may be renewed. Authorisations obtained under ESTA
are valid for the shorter period of 2 years or until your passport expires. After such period,
any granted travel authorisation under ESTA must be renewed
through a brand new application
However, ESTA can be renewed in as short a time as a couple of minutes, so this shouldn’t delay
any of your travel plans, although the U.S. Customs and Border Protection always recommend to
apply or reapply for your ESTA when booking your travel tickets, or at least 72 hours
before your travel date.
You may also re-apply for your ESTA before your current one expires. You may do so at any
time before, on, or after the expiration date of your existing ESTA. If you receive the message
“A valid, approved application with more than 30 days remaining has been found for this passport.
Submitting this application will require payment for this application and will then cancel
the existing application.”, you continue which will cancel the remaining days and replace
it with your new application, which will then be renewed for another 2 years, or until your
passport expires, whichever is soonest.