Building an automatic cloud-based protection system using Vanilla JavaScript, specifically with XMLHttpRequest and the Fetch API, offers a streamlined and accessible approach to securing spreadsheet files. This solution is ideal for lightweight web applications, client-side integrations, and environments where data privacy is critical. By leveraging native JavaScript capabilities, developers can create a responsive, browser-compatible system that applies password protection in real time-without relying on external libraries or server-heavy logic. Supported formats include .xlsx, .xls, .xlsm, .csv, .tsv, .numbers, and more.

In essence, this Vanilla JavaScript solution provides a nimble, cloud-compatible method for automating spreadsheet protection. It empowers developers to build fast, secure, and scalable workflows using only native browser technologies. Whether embedded in a web portal, integrated into a SaaS platform, or used as a standalone tool, this system ensures that spreadsheet content is encrypted and safeguarded-ready for secure sharing, compliance, or long-term storage.