Some countries now require pre-approved travel authorizations for entry, even if you don’t need a visa — for example, the UK now requires an ETA (Electronic Travel Authorisation), while travelers to the US may need an ESTA (Electronic System for Travel Authorization).
These must be obtained before departure and can take time to process, so check the requirements for your destination in advance. Failure to secure the necessary authorization may result in being denied boarding or entry. Kiwi.com is not responsible for obtaining these documents, so be sure to arrange them ahead of your trip.