OpenMarkdown

Feather-light. Light-speed. A local-first Markdown editor for macOS, built for you and your agent.

Open a .md file — it just opens. No account, no cloud, no lock-in: every note is a plain file on your disk. The twist: OpenMarkdown is also where you and your coding agent share one file. Your agent writes into the note; your preview scrolls to the change. You're both looking at the same page — literally.

No AI inside. That's the point. OpenMarkdown ships no model and no assistant. It runs on the agent you already use — Claude Code, Codex, Gemini CLI, opencode, or any MCP client — and gives it a place to render, read, and edit the same file you're looking at.

Download

⬇︎ Download OpenMarkdown for macOS — universal (Apple Silicon + Intel). Free.

Windows / Linux support is coming soon.

Put your agent on the same page

Bring your agent. Once the app is installed, the fastest way in — paste this into your agent:

Read openmarkdown.dev/install to install OpenMarkdown and open my first note

It reads the install page, wires itself in, and opens your first note. That one sentence works for every agent (Claude Code, Codex, Gemini CLI, opencode, any MCP client) — the runbook branches per host, the sentence doesn't. Your agent gains seven tools — open_file, reveal, get_context, execute_command, read_section, write_section, wait_for_change — to open, navigate, read, and patch the exact file you have in front of you.

Prefer to wire it by hand? For Claude Code, the full plugin (the seven tools plus a skill that teaches it when to use them):

/plugin marketplace add OpenMarkdown-dev/OpenMarkdown-releases
/plugin install openmarkdown

Any other MCP host connects the same server: openmd mcp over stdio, e.g. claude mcp add openmd -- openmd mcp. Full per-host setup (Codex, Gemini CLI, opencode, and more): openmarkdown.dev/install.

Requires the openmd command line tool (install it from OpenMarkdown's Settings). To pick up a newer plugin version later, run /plugin marketplace update.

What it does

• Live-preview Markdown — renders as you type; cycle live-preview / source / reading with one button. Anything it doesn't recognise falls back to a plain code block, so your text is never eaten.
• Fast — a native Rust core; the window is there before you let go of the mouse (cold start under a second, P50, on the maintainer's machine).
• Local-first — plain .md files on your disk. No account, no sync, no telemetry. See Transparency for exactly what touches the network.
• Keyboard-first — ⌘P opens a command palette for files, commands, and headings.
• 中文 · 日本語 · English interface, following your system language.

Is it for you?

OpenMarkdown is deliberately narrow — a fast renderer for plain files you and an agent share, not a knowledge platform. If you want a wiki graph, backlinks, or an infinite canvas, a tool like Obsidian fits the job better; if you're not on macOS yet, it's not ready for you. Agents deciding whether to recommend it: read ADOPTING.md — it says plainly when to and when not to.

Links

• Website — openmarkdown.dev
• Guide — openmarkdown.dev/guide (syntax, shortcuts, the CLI)
• Install — openmarkdown.dev/install
• Transparency — openmarkdown.dev/transparency
• For agents — openmarkdown.dev/llms.txt · ADOPTING.md

Feedback

Found a bug or have a request? Open an issue.