Guide
How to open .md files on Windows
A .md file is plain text written in Markdown. Any text
editor opens it, but you only see the headings, tables, and diagrams
as a formatted page in a program that renders Markdown. These are
the common ways to do that on Windows, and what each one leaves out.
Your options
Four ways to read a Markdown file
Notepad
Notepad on Windows 11 can show Markdown with formatting and switch between the formatted view and the Markdown source, as Microsoft describes in its Notepad formatting announcement. That announcement lists bold, italic, links, lists, and headings; Mermaid diagrams are not among them. Notepad is an editor, so the file can be changed by accident.
Visual Studio Code
VS Code has a built-in Markdown preview: open the file and press Ctrl+Shift+V, or Ctrl+K V for the preview beside the source. Its Markdown documentation says the preview renders Mermaid diagrams. It is a full code editor, so reading one file means opening an editor first.
A browser extension
Markdown viewer extensions for Edge, Chrome, and Firefox render a .md file that you open in the browser. In Edge and Chrome the extension can read a file on your disk only after you turn on its access to file URLs in the extension's settings. Support for tables and Mermaid differs from one extension to the next.
A Markdown viewer such as LeanMark
LeanMark opens the file as a formatted, read-only page with GitHub-flavored Markdown tables, task lists, local images, and Mermaid diagrams rendered offline. It cannot edit, and it does not load remote images. The GitHub ZIP is unsigned; the Microsoft Store build is signed by Microsoft.
Files from AI tools
Markdown saved by ChatGPT, Claude, or a coding agent
Chat assistants and coding agents often hand you Markdown: a downloaded answer, a plan, or a README written into a project folder. Opening it in a viewer shows the tables and diagrams instead of the raw symbols.
Keep it open while it is written
When the file changes on disk, LeanMark refreshes the page and keeps your approximate reading position, so you can watch an agent's plan or report grow without reopening it.
Nothing in the file runs
Raw HTML in a document is not run, a strict Content Security Policy limits scripts, and remote images are not loaded. Links to websites open in your browser only after you click them.
Double-click to read
Make .md files open in your viewer
Right-click a .md file, choose Open with, then Choose
another app, pick the program, and select Always. You can change it
later under Settings, Apps, Default apps.
For LeanMark, the optional installer inside the GitHub ZIP adds it
to Open With and to Default Apps for the current user. LeanMark
opens .md, .markdown, .mdown,
and .mkd files.
Measured
What LeanMark costs to open
Median of ten warm launches of LeanMark 0.3.0 with a simple document, counting LeanMark and every WebView2 process it starts.
Measured on Windows 11 Pro build 26200 with an Intel Core i7-13620H, 15.6 GiB of RAM, and WebView2 Runtime 153. Hardware, system state, and document complexity change the result. Linux and macOS are not measured, and no comparison with other programs is claimed.
Read the full measurement- 74.15 ms
- Native window visible, simple document, 0.3.0
- 96.79 MiB
- Peak private memory, full process tree, 0.3.0
Install
Get LeanMark on Windows
winget install abooodbah.LeanMark
winget install --id 9MSS4WKJ22ZV --source msstore
choco install leanmark -y
scoop bucket add lean https://github.com/abooodbah/scoop-bucket
scoop install lean/leanmark
Builds for Linux and macOS are on the releases page. LeanMark is MIT licensed and free.