Proton Authenticator enters the competitive two-factor authentication market as a privacy-focused alternative to established solutions. Developed by Proton AG, the application generates time-based one-time passwords (TOTP) for securing online accounts while maintaining complete offline functionality. The app distinguishes itself through its open-source architecture and adherence to Swiss privacy laws, positioning itself as a premium security tool for users prioritizing data protection. The application's core functionality revolves around generating secure authentication codes without requiring internet connectivity. Users can scan QR codes from supported services to add accounts, with all data stored locally on the device using end-to-end encryption. The app supports multiple account management, organized categorization, and automatic code generation refresh. Unlike cloud-synced alternatives, Proton Authenticator operates entirely offline, eliminating potential attack vectors associated with online synchronization while maintaining cross-device compatibility through secure local backup options. User experience centers around a minimalist interface with clear account organization and intuitive navigation. The main screen displays all added accounts with countdown timers for each TOTP code, while a simple tap reveals the full code for copying. The interface employs security-focused design elements including blurred codes by default and optional biometric authentication for app access. Real-world usage demonstrates reliable performance across various iOS devices, with particular attention paid to accessibility features and system integration. As a newly launched application, comprehensive user reviews are not yet available in public app stores. Early adopters typically report satisfaction with the offline functionality and privacy-focused approach, though the lack of extensive user feedback makes long-term reliability assessment challenging. The absence of cloud synchronization features receives mixed reactions, with some users appreciating the enhanced security while others note convenience trade-offs compared to competing solutions. The application's primary strengths include its robust encryption implementation and complete offline operation, though these features come with the limitation of requiring manual backups for device migration. Proton Authenticator proves most valuable for security-conscious individuals managing sensitive accounts, particularly those already invested in the Proton ecosystem. The app serves as a competent addition to the 2FA landscape, though its niche focus on absolute privacy may limit appeal for users prioritizing convenience features offered by competitors.