The Electronic System for Travel Authorization (ESTA) is a legal requirement for travelers into America. US as part of the Visa Waiver Program (VWP).

The process of obtaining ESTA authorization is preferred to the option of having to apply for an US visa. Not everyone is eligible to travel in the VWP.

ESTA is an electronic security system run through the Department of Homeland Security, Customs and Border Protection.

The ESTA application can be used to determine the your eligibility to travel under the VWP. VWP.  ESTA does not constitute a visa. Neither does it grant permission to travel into the US

To determine if you'll be eligible to apply for ESTA to be eligible, the following criteria are required:  – You are a citizen of a participant VWP nation (such like the UK).

– You have a valid e-passport from a participant VWP country.  – You  are visiting the US by sea or air to visit for business or pleasure,  and you're traveling across US to another destination country (transit)

– you're traveling across US to another destination country (transit). US to another country (transit).  – Your stay will be for no more than 90 days.

Non-US  citizens who travel in the US for not more than 90 days have to be  granted ESTA approval (unless the need for a visa exists)

A  travel permit in accordance with ESTA can only be obtained when you  plan to travel through the US by sea or air in the Visa Waiver Program.

The most common exemptions are for traveling to the US via land, whether or sea from Mexico as well as Canada

If you are able to obtain an approved visa for travel to the US then you don't have to apply for ESTA. Initial security checks be conducted in connection with the visa application.

ESTA applications must submitted online. It is possible to apply on an individual basis or on an aggregate basis.