Whether you clear customs during a layover depends on your nationality, the country you are transiting, and if your journey is on a single ticket. In most of the world (Europe, Asia, Middle East), if you remain in the "sterile" international transit area and your bags are checked through to your final destination, you do not clear customs. However, the United States and Canada are major exceptions; they typically require all international arrivals to clear both immigration and customs at their first port of entry, even for connecting flights. If you are "self-transferring" on separate tickets, you must always clear customs to collect your bags and re-check them. New for 2026, many travelers from visa-exempt countries will also need an ETIAS authorization to transit through 30 European countries. Generally, if your layover is under 24 hours and in a single terminal outside North America, your luggage is transferred automatically, and you avoid the customs hall entirely.