Folio

A fast, good-looking Markdown viewer and editor for macOS, Windows and Linux.

Folio opens your .md files with a clean live preview, lets you edit them in a proper code editor, and turns them into polished PDF or HTML documents. It also handles plain text, code, HTML and images, so it works well as an everyday "open this file and show it to me nicely" app — not just for Markdown.

Built with Tauri 2, so it's a small native app rather than a browser in disguise.

Grab the installer for your platform from the Releases page:

Folio isn't signed with a paid Apple/Microsoft certificate, so on first launch your OS shows a scary-looking warning. This is expected — here's how to get past it once:

• macOS — right-click Folio.app → Open → confirm Open in the dialog. If it still refuses ("Folio is damaged"), run once in Terminal:

  xattr -d com.apple.quarantine /Applications/Folio.app

• Windows — on the SmartScreen screen, click More info → Run anyway.

You only have to do this the first time.

Read comfortably

• Live GitHub-Flavored Markdown preview: task lists, tables, footnotes, frontmatter
• Mermaid diagrams rendered right in the page
• Light and dark theme, plus a whole set of view themes you can switch between
• A document outline (table of contents) you can click to jump around
• Full-text search inside a single file, or across your whole workspace

Edit properly

• Three layouts you switch anytime: View, Edit, and Split (editor + live preview side by side)
• A real editor under the hood (Monaco, the one from VS Code) with syntax highlighting, minimap and multi-level undo
• A formatting toolbar for bold, italic, headings, lists, links and tables — with a built-in cheat sheet if you forget the Markdown syntax
• Paste an image straight from the clipboard and Folio saves it next to your document and inserts the link for you

Keep your files organized

• A Vault sidebar: browse folders, pin the ones you use most (drag to reorder), and jump back to recent files
• Open several files at once in tabs — reorder them by dragging, and Folio remembers them for next time
• Files ignored by .gitignore are dimmed so your working tree stays readable

Export something you can share

• Export to PDF or HTML with an optional cover page, headers/footers and proper code syntax highlighting
• Pick from built-in export layouts, or design your own theme in the in-app theme editor with live preview
• Share themes as .mdtheme files, or let the built-in AI theme author design one for you

Let AI help (optional)

• Translate a document into one or more languages — your code blocks are protected so they come back untouched
• AI actions: summarize, reformat, proofread, extract action items, build tables — with an editable prompt and a diff review so you always see the changes before they're applied
• Bring your own provider and API key; keys are stored separately and never leave your machine except to call your chosen provider

Handle more than Markdown

• Code and text files open read-only with syntax highlighting
• HTML files render in a sandboxed preview
• Images (PNG, JPG, GIF, WebP, SVG, BMP, ICO, AVIF) are shown scaled to fit

Rendered Markdown with GFM tables, syntax-highlighted code and Mermaid diagrams:

Light and dark theme:

1. Open a file — drag a file onto the window, or use File → Open (Ctrl/Cmd+O).
2. Switch how you look at it — Ctrl/Cmd+1 for View, 2 for Edit, 3 for Split.
3. Pin a folder — open a folder in the Vault sidebar on the left and pin it so it's always one click away.
4. Export — File → Export… to turn the current document into a PDF or HTML file.

On Linux you can also register Folio's icon for .md files in your file manager (no sudo needed):

scripts/install-folio-icons.sh

On macOS use Cmd instead of Ctrl.

Folio follows your system language automatically and ships in nine languages: English, German, Spanish, French, Portuguese (Brazil), Italian, Russian, Simplified Chinese and Japanese. To pin one instead, go to Settings → General → Language — the change applies on the next launch.

Folio is a Tauri 2 app: a Rust backend (src-tauri/src/) with a TypeScript frontend (src-tauri/web/) using the Monaco editor. Markdown is rendered by comrak; the shipped frontend bundles live in src-tauri/dist/ and are checked in.

Prerequisites: Rust 1.80+, the Tauri CLI (cargo install tauri-cli), and on Linux libwebkit2gtk-4.1-dev. Node.js 18+ is only needed if you change the frontend.

cd src-tauri
cargo run                      # build + launch a debug build
cargo tauri build              # release binary + installers (DEB/RPM/AppImage on Linux)

Rebuild the frontend bundles only after editing src-tauri/web/:

cd src-tauri/web
npm install                    # once
npm run build                  # typecheck + bundle into ../dist/

cd src-tauri
cargo test                                 # Rust unit + integration
cargo clippy --all-targets -- -D warnings
cargo fmt --check
cd web && npm test                         # frontend (Vitest / jsdom)

The end-to-end suite (48 scenarios, Python + Pillow, visual regression) runs headless on Linux via Xvfb:

bash scripts/run-e2e.sh

For E2E testing, Folio exposes a loopback-only HTTP server on 127.0.0.1:9876. It is always on in debug builds and requires FOLIO_AUTOMATION=1 in release builds. It's bound to localhost with Host- and Origin-header allowlists. The full route list and contract are documented in docs/automation-contract.md.

Architecture notes and feature specs live in docs/; contributor conventions are in CLAUDE.md; open tasks are tracked in TODO.md.

MIT — see LICENSE.