editmd

What it is

editmd is a native macOS markdown editor designed for writers and developers who work with AI agents. It provides a simple WYSIWYG interface that saves files as markdown, allowing users to edit documents while maintaining their preferred markdown format.

The key innovation is real-time collaborative editing powered by Y.js CRDT technology. When AI agents or other programs edit files simultaneously, editmd merges changes in real time without conflicts. Users can continue working while agents make modifications, and undo history only applies to the user's own changes, never to agent edits.

The application is built as a native AppKit document app with a WebKit view running Milkdown editor. It bundles all dependencies so nothing loads from the network. Documents autosave one second after typing stops, and the editor preserves file encoding, line endings, YAML/TOML front matter, and reference-style links. It supports GitHub Flavored Markdown with tables, task lists, strikethrough, footnotes, and mermaid diagrams.

Security is built in: external documents are safe to open, Cmd-click on links never launches applications, and remote images are blocked until explicitly allowed.

Questions from the bench

How do I install editmd?

Install via Homebrew with `brew install --cask kirahowe/tap/editmd` on macOS 14 or later. The cask automatically clears the quarantine flag. Alternatively, download the zip from the release page and run `xattr -dr com.apple.quarantine editmd.app` before opening.

How does editmd handle files edited by other programs while open?

editmd uses Y.js CRDT to diff the new text against the last version, replays differences as edits block by block, and lets Y.js merge them with your unsaved changes. Edits to different paragraphs, list items or table rows combine cleanly, and undo history only applies to your own changes.

What markdown flavors and features are supported?

editmd supports GitHub Flavored Markdown including tables, task lists, strikethrough, footnotes, and heading anchors. It also renders mermaid diagrams with live preview. You can toggle between WYSIWYG and raw markdown view.

Is editmd safe to use with untrusted documents?

Yes. Cmd-clicking links never launches anything—text files open in editmd and other files are shown in Finder. Remote images are blocked by default like in Mail, preventing tracking pixels and information leaks.