Use card for most payments
Visa/Mastercard and contactless phone payments are widely accepted.
Usually not. Cards and contactless payments work almost everywhere — but a small amount of Polish złoty is useful as backup.
SHORT ANSWER
Restaurants, supermarkets, hotels, pharmacies, petrol stations and most tourist businesses normally accept card or contactless payment.
Visa/Mastercard and contactless phone payments are widely accepted.
You do not need a large amount — just enough for the occasional cash-only situation.
Poland uses PLN, not EUR. If a terminal offers PLN or your home currency, usually choose PLN.
WHEN CASH CAN HELP
A few still use coins or simple cash payment.
Some temporary or very small sellers may prefer cash.
A tiny café, kiosk or seasonal stand can occasionally be cash-only.
A little cash is handy if a payment terminal is temporarily unavailable.
There is no fixed amount. For most visitors, a small backup amount in PLN is enough because everyday card acceptance is very good.