Electronic System for Travel Authorization, an online application you must fill if you wish to travel to the US under the Visa Waiver Program. This tag is about the application; for the program itself, use the tag [us-visa-waiver-program].
The Electronic System for Travel Authorization (ESTA) is a United States government requirement (mandated by the Implementing Recommendations of the 9/11 Commission Act of 2007) for participating travelers from Visa Waiver Program (VWP) countries. The ESTA is available for travelers from participating countries arriving by air or sea, to complete online the I-94W form (formerly paper-based and filled on arrival by participating VWP citizens) in advance of travel to the United States. ESTA is not needed when arriving by land from Canada or Mexico.1 Passengers (including babies) without an ESTA may be denied check in, although it is possible to get one while at the airport. Since 2010, a payment of US$14 is required to obtain the ESTA.
Use this tag for questions about the online application (e.g. what to put in a specific field, etc.). For questions about the Visa Waiver Program itself (e.g. entering under it, valid travel purposes and length, etc.) use the tag us-visa-waiver-program).