Validity period of ESTA
The ESTA authorization is valid for two years (and not 3 years as the future ETIAS) from the date of authorization. Thus, travelers who have obtained it may consider making several trips to the United States during this period: they will not have to re-apply for a document each time they travel. However, you will need to ensure that the validity of your ESTA if you have any doubt about the date of its obtaining.
If it is valid for multiple trips, an ESTA authorization is strictly associated with a valid passport number. If your passport expires during these two years, your ESTA form is no longer valid and will have to be re-applied (or renewed).
Travelers who have changed their name, gender or nationality during these two years must also apply for a new ESTA application because their personal information is no longer up-to-date and therefore no longer valid (an update is not possible) . A new request is also necessary if the answers to the personal questions (health, judicial past, behavior) have changed.
Warning : an ESTA authorization is valid for two years but does not allow you to stay in the US for 24 consecutive months. You can stay in the USA for up to 90 days . For stays of more than 90 days, a visa or a green card will be required. Similarly, if your ESTA is pending , you can not enter US territory.
Good to know : If your ESTA form expires during your stay in the United States, you can complete your stay with confidence and have no problem when leaving the territory.