Gmail Cleaner is a self-hosted, privacy-focused web application for bulk Gmail management. It allows users to unsubscribe from mailing lists, delete emails by sender, mark emails as read, archive, and manage labels—all via a FastAPI backend with a vanilla JavaScript frontend. The architecture follows a modular service layer: each Gmail operation (scan, delete, mark-read, unsubscribe, etc.) lives in its own file under `app/services/gmail/`, coordinated by an in-memory `AppState` singleton. Background tasks handle long-running operations, and the frontend polls status endpoints to show progress. Authentication uses Google OAuth 2.0 with two modes (local desktop web server and manual URL copy for Docker). The tool is designed to run 100% locally, with no external data collection, and uses batch Gmail API requests (100 per call) for efficiency. The codebase includes comprehensive unit tests, integration test plans, and CI/CD via GitHub Actions.