Buttercup Password Manager is an open-source tool available on various platforms, including iPhone. It securely stores and manages login information for personal or work-related services in encrypted archives. With Buttercup, users can organize their credentials in groups and entries for easy management. The program offers a desktop application and browser extension for seamless access across different platforms.

Key features of Buttercup Password Manager include storing unlimited login details, saving archives to various storage providers, autofill for login forms, OTP/2FA code support, quick site access, auto-locking archives for security, fingerprint or FaceID authentication, and the ability to add multiple archives. Additionally, the app ensures privacy by not sending any user or archive information to external services and refrains from using in-app analytics, relying instead on anonymous service analytics provided by Apple and Google.