Before you can travel to the United States for less than 90 days, you must complete an ESTA application online via the official ESTA form. This procedure allows the U. S. government to assess whether or not you are a potential danger to U. S. citizens. Once you have obtained your authorization, you will be able to travel to the USA without a VISA.
Simply show your copy with the words "Authorized" at the airport or port with your passport to board. For this reason, it is necessary to print this last one.
As long as the form has been completed online and your request has been granted in the same way, the U. S. Department of Homeland Security is able to communicate your status to whoever you are, regardless of your mode of transportation. With specialized software, it will be enough for those in charge to integrate your passport to obtain your "Status". Therefore, you are not obliged to print your form or to have your authorization in any place. As a general rule, if you have the reference number of the latter, it will be more than enough.
The ESTA authorization is not obligatory, but it is strongly recommended, if only for safety reasons. It is not impossible that checking your status at border crossings will take time, and computer problems are not excluded, which could delay your boarding.
The presentation of this document gives you direct access to the information to be verified and saves you time. You should also be aware that unlike airlines, some means of transportation may not have specialized software that makes electronic verification impossible.
In such cases, if you do not have the reference number of your form, it is quite possible that you will be denied boarding. Having this authorization at your disposal also avoids you complications during your other stays, because first of all it will allow you to determine how many days you are still entitled to. But it will also allow you to prove that your ESTA is still valid if you wish to return to the United States. As a reminder, ESTA is valid for two years (or until the expiry date of your passport).
In addition to the printed document, always keep a record of your authorization reference number somewhere in your wallet or smartphone. If you forget to give official authorization, this will make it easier for the inspectors to check your status.
If you do not have this information at your disposal, you can also log back on to ESTA's official website and print it out if possible. If not, you can simply write down the identification number and provide it to the responsible parties.