Croatian citizens [have been eligible for ESTA since December 1, 2021](https://www.federalregister.gov/documents/2021/09/30/2021-21136/designation-of-croatia-for-the-visa-waiver-program), so even if you did not have a visa, you could use your new Croatian passport to apply for ESTA. However, since you do have a valid visa issued in your old Croatian passport, you should not apply for ESTA with your new Croatian passport. ESTA enables you to travel under the visa waiver program, but you do not need a waiver because you have a valid visa. Instead, you should travel with both passports: the valid one and the expired one that contains the valid visa. As to veracity, here is what the US government itself has to say about it (from the FAQ page [About Visas - The Basics](https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/frequently-asked-questions/about-basics.html)): > My old passport has already expired. My visa to travel to the United States is still valid but in my expired passport. Do I need to apply for a new visa with my new passport? > > No. If your visa is still valid you can travel to the United States with your two passports, as long as the visa is valid, not damaged, and is the appropriate type of visa required for your principal purpose of travel. (Example: tourist visa, when your principal purpose of travel is tourism). Both passports (the valid and the expired one with the visa) should be from the same country. When you arrive at the U.S. port-of-entry (POE, generally an airport or land border) the Customs and Border Protection Immigration Officer will check your visa in the old passport and if s/he decides to admit you into the United States they will stamp your new passport with an admission stamp along with the annotation "VIOPP" (visa in other passport). Do not try to remove the visa from your old passport and stick it into the new valid passport. If you do so, your visa will no longer be valid. If you do decide to use the visa, I would recommend presenting the two Croatian passports together to the US immigration officer, with the old one open to the visa page and the new one open to the main data page, to help the officer recognize more quickly that you are applying for admission with a B visa rather than through the VWP. Sretan put! --- Also see [Frequently Asked Questions about the Visa Waiver Program (VWP) and the Electronic System for Travel Authorization (ESTA)](https://www.cbp.gov/travel/international-visitors/esta/frequently-asked-questions-about-visa-waiver-program-vwp-and-electronic-system-travel): > Do I need to apply for ESTA if...? > > I have a current, valid visa? > > Individuals who possess a valid visa will still be able to travel to the United States on that visa for the purpose for which it was issued. Individuals traveling on valid visas are not required to apply for an ESTA authorization. --- You also ask: > I just read that some sites don't actually "scam", but just charge extra, but still result in you receiving a valid ESTA approval. If that is the case, would it conflict with the ESTA application I submitted myself, afterwards? Is there a consequence to applying twice? It's perfectly fine to have a valid ESTA and a valid visa. In your case this would mean that you can choose to travel with the visa by using your Croatian passports or with the ESTA using your German passport. You can even have a valid ESTA for each of your passports (though CBP recommends against it to avoid the possibility of confusion and delay). As Hilmar notes in a comment, application for a subsequent ESTA should result in cancellation of any prior ESTA authorization for the same passport. But I would recommend, if you have submitted more than one, to double check before traveling that at least one of them is still valid. You shouldn't really need to keep track of which one it is. As Hilmar also notes, a traveler with a visa has more rights than a visa waiver traveler. The only rights that are likely to matter are the period of admission (a default of six months vs. an absolute limit of 90 days) and being able to apply to extend or change your nonimmigrant status without having to leave the country. These rights matter to very few tourists. (The most prominent right that matters to almost nobody is the right to demand a hearing before an immigration judge if you are refused entry or identified for removal -- i.e., deportation. Most tourists won't be in either category, and most of the few who are will be unlikely to want to challenge the decision before an immigration judge.)