After obtaining your ESTA authorization, you can travel to the United States as many times as you wish for periods of up to 90 days during the validity period of your ESTA. Once you leave the country, this 90-day period is usually reset.
We take the example of a person who travelled to the United States under the Visa Waiver Program for a month, then returned to France for a period before leaving, this ESTA “clock” returns to zero. When this person wants to go back to the United States, he or she will have 90 days of access.
However, there are exceptions to this rule. If you travel to adjacent islands, Mexico or Canada as part of your trip to America, the time spent in these places will always be part of these 90 days. It is mainly to prevent them from going to Mexico or Canada after three months to “reset the clock”. Remember, if for any reason you need to spend more than 90 days in the United States, you will need to apply for the visa for your trip.