Spending the night at the airport
Keflavík airport is small and opens around the clock. Although staying inside the enclosure during the night is discouraged (you will even see many warning signs inside the terminal), the airport staff generally won't bother sleeping passengers, although they will wake everyone up at around 4:00 am. The place, although quiet at night, is pretty cold and bright, so it is recommended to have a sleeping bag, blankets and a mask.
Where to rest: You can find some benches to lay down, but these are scarce, so your only option will probably be the floor. Depending on your airline and flight class, you could also enter the airport's VIP lounge, which remains open 24 hours a day between May and October. On the other hand, there is a hotel 100 meters away from the terminal.
Baggage: Between May and September there is a left-luggage service that operates 24 hours a day. At other times of the year it closes at night.
Eating and drinking: Eateries only operate during flight hours.
Restrooms: There are showers inside the VIP lounge, but not inside the public toilets.
Wi-Fi: Free and unlimited.
Other services available around the clock: Bank, ATMs, children's play area, baby changing facilities.
The Airport Hotel Aurora Star (Tel +354 595 1900) is found 100 meters away from the terminal. There are more options nearby, some of them with transfer services for their guests. Alex Guesthouse (Tel +354 421 2800), Park Inn by Radisson Reykjavik Keflavik Airport (Tel +354 421 5222), Hotel Keflavik (Tel +354 420 7000), Hotel Berg (Tel +354 422 7922), Bed & Breakfast Keflavík Airport Hotel (Tel +354 426 5000), Whitehouse B&B (Tel +354 864 2596), Home Guesthouse (Tel +354 897 1827), B&B Guesthouse (Tel +354 421 8989), Little White Castle (Tel +354 861 6811).