Oasis Handy Folder is a portable Windows application for browsing folders and reading or editing files in place. It displays Markdown with formatting and can also open and make changes to HTML, JSON, plain text, and code files. It is designed as a lightweight companion for checking and making quick corrections to files, rather than as a full-featured editor. Users can open a folder, review documents such as notes, plans, reports, and README files, and edit them without moving them elsewhere. The app also supports printing and translation, along with everyday folder and file operations. The package is approximately 36 MB and runs from a folder, including from a USB drive, without installation or administrator rights. The first time a user runs a command or folder tool, the app asks for permission. Windows may show an unknown publisher warning because oasis.exe is not code-signed. Handy Folder is built with Oasis, a system that wraps an HTML page as a Windows desktop app and provides a JavaScript API for file access and other functions within a permission-controlled sandbox. Documentation is available in English and Traditional Chinese, and the app’s manual can also be opened by pressing F1. The project is distributed under the MIT license.