The "Epitech Calendar Sync" browser extension was born from a concrete need shared by every Epitech student: keeping track of an ever-changing academic schedule across multiple calendar platforms. Designed and developed entirely by myself, this Chrome and Firefox extension automatically fetches registered events from the Epitech Intranet and synchronizes them in real time with Google Calendar, Outlook, and Apple Calendar. Built with JavaScript ES6 Modules on the Manifest V3 architecture, it leverages OAuth2 with PKCE for secure, seamless authentication against both Google and Microsoft APIs, while all data processing remains entirely local within the browser — no external server, no data collection. The extension features smart event deduplication through unique UID generation, automatic cleanup of unregistered events, configurable background synchronization with proactive token refresh, and event filtering with color-coding by type. Its interface, structured around a clean three-tab popup, offers an intuitive experience for connecting services, launching syncs, and fine-tuning preferences such as sync intervals, event filters, and calendar colors. Beyond solving a daily pain point for students, this project showcases my ability to architect a complete, privacy-first product — from OAuth flows and REST API integrations to polished UI and robust error handling — while navigating the constraints of browser extension development. Privacy policy : https://docs.google.com/document/d/1lBcr4wmL-upxpootNujWvDb6DsyDuxsqFNCPaVlsBo4/