Yes, you can generally leave the airport during an international layover in 2026, but it is a legal entry into the country, not just a "step outside." To do so, you must pass through Immigration/Passport Control, which requires a valid visa or visa-waiver (like ETIAS for Europe or ESTA for the US). For layovers under 6 hours, it is rarely recommended, as clearing customs twice and returning through security can take 3+ hours. However, hubs like Singapore (Changi), Doha (Hamad), and Seoul (Incheon) actively encourage this by offering free city tours for passengers with layovers longer than 5–8 hours. In the US, all international passengers must clear customs at their first point of entry anyway, meaning you are "legally in the US" during your layover and can walk out of the front door immediately. Always verify if your destination requires a "Transit Visa" specifically for leaving the terminal, as rules changed significantly for several Asian and African hubs in 2025.