Open .md files on a Mac as documents, not source code.

All four work today, on any Mac, and none of them costs anything to try. Only two of them show you a document instead of syntax.

If you are already in the folder, opening a file from the command line is faster than going back to Finder. The open command is built into macOS and hands the file to a Mac app rather than printing it in the terminal.

open -a Imark notes.md    # open it in a named app
open notes.md             # open it in whatever app owns .md
open -e notes.md          # open it in TextEdit, as raw text
open -t notes.md          # open it in your default text editor
open -R notes.md          # reveal it in Finder instead of opening it

Once you have chosen, tell Finder about it: select a Markdown file, press Command-I for the Info window, choose the app under Open with, then click Change All and confirm. Every .md file opens there from then on, including ones you double-click inside a cloned repository. Change All is the step people miss — without it you have changed one file, not the file type.

On a Mac with Xcode installed, Markdown files get Xcode's icon, open in Xcode on a double-click, and show as source code with line numbers in the Finder preview. Nothing is broken. Xcode registers itself as a handler for .md when it is installed, and because it is the newest app to claim the type, it wins. It happens to people who have never opened Xcode on purpose, because installing the command line developer tools or a large IDE update can pull it in.

Markdown never settled on one extension, so the same kind of file arrives under half a dozen names. All of them are plain text and all of them hold the same syntax; only the ending differs, and the ending is what decides which app opens the file.

A viewer is not a replacement for your editor. Leave the document open in Imark on one half of the screen while you write in Cursor, VS Code, Zed or Vim on the other. The rendered view follows every save and holds your reading position, so you are not scrolling back after each change. This is also the answer for a file an AI coding agent is writing while you watch: the document updates as it goes.

The files that most need a real viewer are the ones full of structure: GitHub-flavored tables, task lists, syntax-highlighted code, Mermaid diagrams and KaTeX maths and local images. That is where TextEdit stops being enough, because a wide table becomes a wall of pipe characters and a diagram becomes twenty lines of code. Imark renders all of it, in the window and in the Finder preview, offline and for free.