The lek, the only official currency
The country's currency is the lek. It is the only legal tender, and it is what prices are shown in as soon as you step outside the busiest tourist areas. One quirk throws visitors: prices are often quoted in old lek, a habit left over from a currency reform, which produces figures ten times higher. When a number looks absurd, that is usually why.
Euros are accepted, but they cost you
In the tourist areas of Saranda and Ksamil many places accept euros. They then apply their own conversion rate, which will never be the market rate, and your change often comes back in lek. Paying in euros is therefore convenient and consistently more expensive. Fine to get you out of trouble, a bad habit over a full week.
Cards: where they work, and where they do not
Hotels, established restaurants and supermarkets take cards without trouble. Small bars, beaches, taxis and village shops run on cash. The rule that saves grief: never head out for the night relying on a card alone, and keep enough cash for the ride home. That is what people most often lack at four in the morning.
Withdraw locally rather than exchange beforehand
Changing money at home before you leave almost always gives a worse rate than withdrawing on arrival. At the machine, two reflexes: refuse the conversion the screen offers, which uses an unfavourable rate, and prefer one large withdrawal to several small ones, since fixed fees repeat with every transaction. Those two habits save most of what people usually lose.