This case study explores how Kiwix, a non-profit organization, uses Progressive Web App technology and the File System Access API to enable users to download and store large Internet archives for offline use. Learn about the technical implementation of the code dealing with the Origin Private File System (OPFS), a new browser feature within the Kiwix PWA that enhances file management, providing improved access to archives without permission prompts. The article discusses challenges and highlights potential future developments in this new file system.