Should I exchange currency before travelling?

Generally you will do better withdrawing local currency from a bank machine at your destination, or paying by card, than exchanging cash at an airport bureau. Airport exchange counters have captive customers and their rates reflect it.

The underlying reason is that the headline rate is not the whole cost. Exchange services build their margin into the rate itself, so a zero-commission sign can still be expensive. Comparing against the mid-market rate, the figure you see quoted in the news, reveals the actual spread.

Cards issued specifically for travel, which apply the network rate without a foreign transaction fee, are usually the cheapest route. Ordinary cards frequently add a percentage on every foreign purchase, which accumulates quietly.

One trap is worth knowing specifically. When a foreign card machine or cash dispenser offers to charge you in your home currency, that is dynamic currency conversion, and the rate applied is set by the merchant's provider and is almost always worse than your own bank's. Always choose to be charged in the local currency.

Carrying a small amount of local cash for arrival remains sensible: for transport, tips, or places that do not take cards. A modest sum obtained before departure at a reasonable rate, or from a bank machine on arrival, covers this.

Cash acceptance varies enormously by country, and the assumption that cards work everywhere fails in several places and in the opposite direction in others, where cash is increasingly refused. Checking what is normal at your destination is worth two minutes.