Dev File Viewer

Preview Markdown, source code, and diffs locally with outline navigation, a directory tree, and themes. 100% offline and private.

Dev File Viewer is a privacy-first viewer for the files developers read every day: Markdown, source code, diffs, and plain text. Everything is rendered locally inside the extension — file contents never leave your machine. RENDERING • Markdown with GitHub-flavored syntax, tables, and stable heading anchors • Mermaid diagrams rendered from mermaid fenced code blocks • Source code with syntax highlighting for dozens of languages, plus common extensionless files (Dockerfile, Makefile, Gemfile, Rakefile, and more) • Diff / patch viewer for .diff and .patch files, with unified or split view • Plain text with line-ending detection NAVIGATION • Outline / table of contents generated from headings, available as a sidebar tab or a low-distraction floating popover • Draggable, pinnable floating Outline button • Directory tree sidebar for a folder you select • Multiple file tabs with pin and close CUSTOMIZATION • Themes: System (light/dark), Bloom, Forge, and Folio • Adjustable content width (Narrow, Comfortable, Wide, Full) and text size • Optional per-file scroll-position memory (current browser session only) • Resizable, collapsible sidebar with persisted layout PRIVACY • 100% client-side: the parser, sanitizer, renderer, and Mermaid are all bundled inside the extension • No tracking, no analytics, no data collection • No broad web access by default — access to http/https pages is optional and only granted if you enable it in Settings OPEN SOURCE Licensed under GPL v3. Source code, issues, and feature requests: https://github.com/yhchiu/dev-file-viewer