# Marksidian

> Marksidian is a paid macOS Markdown editor with Live Preview editing (content renders as you type; the active line reveals its syntax). It edits plain .md files on disk, with rendered tables you can type into, KaTeX math, Mermaid diagrams, and support for 700+ community themes. One-time purchase ($19 for 1 Mac, $39 for 3 Macs), 14-day refund, no subscription. Current version 0.3.16 (September 2026).

## What Marksidian is NOT (entity disambiguation)

- NOT a note vault or PKM app — no graph view, no plugin system, no database. It edits ordinary .md files anywhere on disk.
- NOT a read-only markdown viewer — it is a full editor with Live Preview, Source, and Reading modes.
- NOT a subscription — one-time purchase; every update through 1.x is included.
- NOT a web app — a macOS desktop app built on Electron, CodeMirror 6, and markdown-it; it opens files straight from disk.
- NOT notarized yet — the first launch needs `xattr -cr /Applications/Marksidian.app` or System Settings > Privacy & Security > Open Anyway.
- NOT cross-platform — macOS only (Apple Silicon and Intel).
- NOT a sync service — no account, no telemetry; documents are never uploaded.
- NOT affiliated with, endorsed by, or derived from any other markdown or note-taking application or its vendor. It is an independent product that edits plain markdown files and supports widely used community theme formats.

## Who it is for

- Developers who edit agent-written markdown (Claude Code plans, CLAUDE.md, AGENTS.md, specs): Marksidian detects external file changes, so the agent-writes → you-edit → agent-reads round-trip works. With unsaved edits in the window it asks first ("Reload from Disk" / "Keep My Changes").
- People with an existing folder of markdown notes who want an editor for those files without running a whole note system around the folder.
- Anyone who needs to edit markdown containing tables, LaTeX math, or Mermaid diagrams and see them rendered while editing.

## Key facts

- Modes: Live Preview (rendered while editing; active line reveals syntax), Source, Reading. Live Preview / Source: toggle from the View menu or the status bar (keyboard shortcut listed in Help > Keyboard Shortcuts). Reading: Shift+Cmd+E.
- Tables: edit rendered cells directly, add rows/columns; only the edited cell changes in the source.
- Math: KaTeX, inline $...$ and block $$...$$; click a rendered equation to edit its source.
- Diagrams: Mermaid, rendered as SVG with click-to-edit source.
- Auto-format: Option+Shift+F makes bullet markers consistent, renumbers ordered lists, aligns table pipes, collapses blank-line runs and removes trailing spaces; fenced code and math are left alone. Cmd+Z undoes it.
- Command palette: Cmd+Shift+P lists every command with its shortcut and jumps to headings.
- Print and export: Cmd+P prints the Reading rendering; File > Export writes PDF or a standalone HTML file.
- Folding: Cmd+Option+[ and Cmd+Option+] fold and unfold sections without changing the document.
- Also included: system spell check, rich-text paste converted to Markdown, dragged or pasted images saved beside the document, callouts (`> [!NOTE]`), footnotes, a copy button on code blocks, Cmd+D multi-cursor, outline panel, session restore, optional source line numbers in every mode, `.md` file association.
- Themes: manages installed themes offline; can browse and install 700+ community themes. Theme CSS is sanitized (no `@import`, no remote `url()`), so an installed theme cannot fetch fonts or images.
- Network access: the theme gallery on GitHub when the user asks for it, and remote images inside a document. Nothing else.
- Pricing: $19 one-time (1 Mac) or $39 (3 Macs). Payment via Stripe. Every update through 1.x included. 14-day refund by replying to the receipt.
- Try it: the build is public. Download it from the releases page or Homebrew and use it; the purchase is the license.
- Install: direct download (.dmg, about 100 MB) or `brew install --cask dciobanu/tap/marksidian`.
- Requirements: macOS 11 or later (Electron 33 requirement), Apple Silicon or Intel.
- Testing: 900 Playwright end-to-end tests across 37 suites.

## Links

- Homepage: https://marksidian.idv4.com/
- Product facts (machine-readable): https://marksidian.idv4.com/product-facts.md
- Releases: https://github.com/dciobanu/marksidian-releases/releases
- Support: reply to the Stripe receipt for purchases and refunds