This paper presents CODEGEN, an advanced React-based online coding platform offering real-time code execution and highly customizable user experiences. Built using ReactJS and CodeMirror, it supports multiple programming languages such as C++, Python, Java, and JavaScript. The platform integrates with Judge0 API for seamless code execution and includes robust features like user authentication, multi-theme support, and file management. Unique features such as Top Coding Questions, Dashboard Analytics, and a Chatbot Helpdesk provide additional functionality, making CODEGEN a powerful tool for learners and professionals. This paper explores the platform’s architecture, innovative features, and impact on software development education.