US authorities have developed a new electronic travel authorization program that has been in effect since 12 January 2009. Since then, all citizens of Visa Waiver countries who want to travel to the US under the Visa Waiver Program need an approved ESTA prior to boarding a plane or ship to the US.
In practice, this means all VWP travelers (including babies and children) have to fill out an application with personal and other data online. This website is currently available in 14 different languages.
Based on the submitted information, each traveler’s eligibility for visa-free travel will be determined. The information collected is the same as that on form I-94. ESTA applications can be submitted any time prior to travel. It is, however, advisable to apply as early as possible, at the very least 72 hours before departure (emergencies and last-minute travel will still be accommodated).
Should there be any changes concerning destination address or other travel data, you can update your application on the website.
In most cases the ESTA system should respond to an application very quickly. Possible replies can be: authorization approved, travel not authorized, or authorization pending.
An approved ESTA travel authorization is valid for two years or until your current passport expires, whichever comes first. It is also valid for multiple entries into the US. Please note, however, that even an approved travel authorization via ESTA does not guarantee you admission into the US and is only valid for travel under the VWP. It can not serve in lieu of a visa when a visa is required.
Should you submit an ESTA application that is not approved, you will need to obtain a valid visa to travel to the US.