Now US government made it mandatory to apply Esta application online in advance of 3 days of US travel for all US tourists. This mandatory change effects all 35 nations that have US Visa Waiver Status. Here is list of 35 countries with visa waiver status.
Some important notes of the process :
– Approval within minutes of filling out the Esta online form
– No more Greencard forms filling in the plane.
– Once approved Esta valid for two years and can be used for multiple entries into the US.
– The free official Esta from US gov – https://esta.cbp.dhs.gov