Furnished or unfurnished is one of the first choices you make when renting in Spain, and it is also one of the most misunderstood. It affects what you pay, what you are on the hook for, and sometimes what kind of contract you are signing. Here is the honest version.
The thing to get straight early: in Spain furnished or unfurnished does not decide your lease type. The law behind residential letting, the LAU, cares about purpose. A home you live in as your main address is a vivienda lease with strong protections. A place you take for a defined temporary reason is a different animal. Furnishing is a clue, not the rule. Lots of furnished flats sit on full vivienda leases, and plenty of empty ones are let on a temporary basis.
In theory, furniture and appliances included. In practice it can mean anything from a fully equipped home with linen and crockery to a place with a sofa, a bed and a fridge. There is no legal standard, which is exactly why the inventory matters. A proper inventory, signed and photographed, is your only protection over what you are expected to return.
A furnished place in Barcelona typically runs a premium over a comparable empty one:
Whether that premium is worth it depends on how long you are staying. Furnishing a home from scratch costs real money and time, and if you are in Spain for two years it rarely pays to buy a whole house of furniture. If you are settling for good, buying slowly usually wins.
For a long-term vivienda lease the fianza is one month, and additional guarantees are capped at two more, so three months at most when you sign.
Temporary and furnished lets are where it drifts. A temporada contract for a genuine short stay is not under the same cap, so two months of deposit is common, and furnished lets are the ones most often written on that basis. If you are shown a furnished flat with a two-month deposit and a contract that never quite says temporada out loud, slow down and read the purpose clause. That wording, more than the sofa, tells you what you are signing.
A rough steer, not a rule:
Whatever you choose, these are the things that decide whether it goes well: