Firefly III is a self-hosted personal finance management application built on the Laravel PHP framework. It provides comprehensive double-entry bookkeeping with support for multiple currencies, accounts, budgets, categories, bills, piggy banks, recurring transactions, and rules. The system exposes both a full web UI using Blade templates and Alpine.js (with legacy jQuery components) and a RESTful JSON API (v1) for programmatic access. Key features include transaction splitting, budget limits, auto-budgeting, rule-based transaction processing, exchange rate management, webhook integration, multi-user with group administration, and detailed reporting with charts. The codebase follows a repository pattern with interfaces, uses events and listeners for side effects, and includes a substantial set of artisan commands for maintenance, upgrades, and data corrections.