What Markdown Library ML-42 is
Markdown has become the working format of AI tools. Context files, specs, agent output and decision logs are all markdown, yet code editors treat it as one more text file and note-taking apps want to own the files.
ML-42 is a native macOS app for people who work in markdown. Add your project folders, browse them visually, read every file rendered, edit the raw markdown when you need to, and move between projects quickly. Your files stay on disk, in your repos, where they already are.
Installation
ML-42 is a native macOS app, sold on the Mac App Store. It needs macOS 26 or later.
Add your first project
Launch ML-42 and click Add Project in the sidebar, or choose File › Add Project (Cmd+Shift+O). Pick any folder that holds markdown files: a project repo, a docs directory, a notes folder. ML-42 remembers your projects between sessions with security-scoped bookmarks, so the sandbox keeps its access without asking again.
To open a single file instead, choose File › Open File (Cmd+O).
Your project appears in the sidebar with its folder hierarchy, filtered to show only markdown files. Source code, images and config files stay out of the way.
Navigating your files
The sidebar shows your projects as collapsible trees. Click a folder to see an overview with document cards, subfolder counts and recent activity. Click a file to open it.
As you navigate, the sidebar follows, expanding the tree to show where you are. The breadcrumb path at the top of every view takes you back up the hierarchy. Back and forward (Cmd+[ and Cmd+]) work like a browser.
Star important files from the toolbar and they appear in the Favorites section at the top of the sidebar.
Reading and editing
ML-42 has two modes. A file opens in view mode: rendered, with headings, links, code, tables and front matter styled for reading. To change it, switch to edit mode with the toolbar’s Edit button or Switch to Edit in the View menu (Cmd+Shift+E). Edit mode shows the raw markdown with line numbers and edits at native speed. The same shortcut switches back to view mode.
In view mode, code blocks are highlighted in more than 15 languages, tables have aligned columns, and front matter shows as a list of properties.
In edit mode, select text and a floating toolbar appears with formatting options: bold, italic, headings, lists and links. Cmd+B and Cmd+I wrap the selection in bold or italic markers.
Edits are saved to disk automatically after a short pause.
Finding things
Cmd+K opens the command palette (File › Quick Open). It searches all your projects at once, by filename as you type and by content right after. Each result shows its path and whether it is a project, a folder or a document. Use the arrow keys to move and Return to open.
Within a document, Cmd+F opens a find bar with a match count. Cmd+G and Cmd+Shift+G move to the next and previous match.
The inspector
The inspector on the right shows and hides with Cmd+Option+I. For a document it shows a table of contents built from your headings (click an entry to scroll there) and a short summary written on your Mac by Apple Intelligence. For a folder it shows recent file activity in that folder.
Light and dark mode
Click Switch to Dark or Switch to Light in the sidebar, or choose System, Light or Dark in Settings. The document, the code highlighting and the rest of the window follow.
Next steps
- Read the workflow for how the pieces fit together in daily work
- See features for a reference of everything ML-42 does
Markdown Library ML-42
A native Mac reader and editor for the markdown in your repos and docs folders. No import, no vault.
Download on theMac App Store$12.99 once. Introductory price. It goes up later.