How to open a .md file on Mac

Someone sent you a README.md, or an AI tool saved its answer as a .md file. Here is what it is and how to read it properly on a Mac.

What a .md file is

.md means markdown: plain text with a few marks for structure. # Title is a heading, **bold** is bold, lines starting with - are a list. It is the format of READMEs, developer docs, note apps and almost everything AI assistants write.

Option 1: TextEdit or any text editor

Right-click the file, choose Open With → TextEdit. It opens, but as raw text with every symbol showing. Fine for a quick edit, not for reading.

Option 2: a markdown reader

A reader shows the file the way the author meant it: headings, lists, links, tables, code, even diagrams and math. Lumd is a free markdown reader for macOS:

  1. Download Lumd and drag it to Applications.
  2. Double-click any .md file, or drag it onto the Lumd icon.

Make every .md file open in Lumd

  1. In Finder, select any .md file.
  2. Choose File → Get Info (⌘I).
  3. Under Open with, pick Lumd, then click Change All…

Peek without opening

Select a .md file in Finder and press Space. With Lumd installed, Quick Look shows the file formatted, so you can skim it without opening anything.

Questions

What is a .md file?

A markdown file: plain text with simple marks for headings, bold, lists, links and code. Any text app can open it; a markdown reader shows it formatted.

Can TextEdit open a .md file?

Yes, but as plain text. You will see the # and * symbols rather than headings and bold.

How do I make .md files always open formatted?

Install a markdown reader such as Lumd, then in Finder select a .md file, choose File → Get Info, set Open with to the reader and click Change All.