İstanbulkart — Official Istanbul Transit Card App

İstanbulkart is Istanbul's unified contactless transit card, accepted on every public-transport mode in the city: buses, metro, Marmaray, ferries, funiculars, sea buses, and even some intercity buses leaving Istanbul.

The app handles online top-ups (no need to find a kiosk), shows real-time balance, registers student/senior cards for discounts, and now supports digital İstanbulkart in mobile wallets — useful for short-stay tourists.