This Excel Helper utility is designed to generate Excel files in an optimized and flexible manner using the ClosedXML.Excel package. It accepts data in JSON format, dynamically creates column headers based on JSON keys, and populates the worksheet with corresponding records without requiring a predefined schema. The helper also supports adding customized header and footer records to the Excel file through structured row–cell input, allowing static or formatted content to be inserted above or below the JSON-driven data. This makes it suitable for generating reports, exports, and configurable Excel outputs. The implementation focuses on performance and maintainability, leveraging efficient JSON parsing, dynamic column handling, and in-memory stream processing to produce the final Excel binary output ready for download or further processing.