Can ESTA be extended?

It is not possible to extend your ESTA but you are able to renew your ESTA. Your ESTA is valid for a maximum period of two years from issue, or until your passport expires if that is sooner. To renew your ESTA, you must submit a new application,in the same way that you submitted your previous one.
As the ESTA renewal process is usually very quick, it should not cause any delay to your travel plans. However, it is advised by the U.S. Customs and Border Protection to apply or reapply for your ESTA when you book your trip, or a minimum of 72 hours before you plan to travel.
You may also reapply 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 should choose to continue, which will cancel the remaining days and replace it with your new application. The ESTA will then be renewed for another 2 years, or until your passport expires, whichever is sooner.
Re-applying for ESTA is a straightforward process. You will need follow the instructions to answer all of the required questions and submit a new application for travel authorisation, just like you did the first time you applied.