Fylune

Fylune is a free document editor that edits Markdown, MDX, JSON and JSONL files locally on desktop, with offline use and no account needed, and fills official PDF forms in the browser with cloud saving.

Fylune is a document editor that works on two fronts: a desktop app for editing plain files stored on your own machine, and a browser-based tool for filling in official PDF forms. The desktop side opens Markdown, MDX, JSON and JSONL files straight from existing folders, so the files stay ordinary files that Finder, Git and other tools can still read. The core editor does not need an account and keeps working without a network connection. In practice, a user points Fylune at a project folder and gets a file tree beside an open document, with search and navigation across the folder. Pasting an image or adding a video copies the asset into the project next to the Markdown that uses it, and the editor writes the relative path automatically. This removes the usual chore of managing URLs for local media. The Markdown support goes beyond basics: tables, checklists, code blocks and media render live, Mermaid flowcharts and mind maps draw in the preview, and KaTeX handles formulas. MDX blocks are supported too, though MDX and JavaScript are not executed in the preview, which limits what can run inside the editor. The PDF side is separate. Official PDF forms can be filled in the browser and saved to a Fylune cloud account, which is where an account becomes relevant. The homepage describes the core editing as free, with paid plans reserved for optional cloud and advanced collaboration services rather than access to local files. A macOS build is labeled alpha, so it is early software. Fylune fits writers, developers and documentation owners who keep notes, specs and content as files in a repository and want a calmer interface than a full IDE. Compared with cloud-first writing tools, it prioritises local ownership and offline use. Compared with general Markdown editors, it adds MDX and JSONL handling plus form filling. Anyone needing heavy real-time collaboration should check what the paid tier actually covers.