What does MD stand for?

Markdown. The .md extension marks a plain text file written in Markdown, a lightweight way of adding formatting — headings, lists, links, emphasis — using ordinary punctuation.

A plain text file whose contents follow Markdown conventions. There is nothing binary or proprietary inside it: open it in Notepad or TextEdit and you see exactly what the author typed, punctuation and all.

How do I open an .md file?

Any text editor opens it, because it is text. To see it formatted rather than raw you need something that renders Markdown — this site does that in your browser, with no install and no upload.

What is the difference between .md and .markdown?

Nothing. Both extensions mean the same thing and every tool treats them identically. .md is shorter and far more common; .mdown and .mkd also appear occasionally.

Can I convert an .md file to Word or PDF?

Yes. Open it here and export to PDF, Word or HTML from the Export menu. All three conversions run in your browser, so the file is never uploaded.

Why is Markdown used so widely?

Because the source stays readable. A Markdown file is legible as plain text, diffs cleanly in version control, and will still open in fifty years — none of which is true of a binary word processor format. It is also the format large language models write in by default.

What is an .md file?

MD stands for Markdown. An .md file is a plain text file that uses ordinary punctuation to mark up formatting — a # for a heading, an asterisk for a bullet. Nothing else is inside it.

The source on the left is exactly what is in the file

Markdown

Result

Runs entirely in this tab. Open the full editor to work on a real document.

What is actually in the file

Open an .md file in Notepad or TextEdit and you see what the author typed, punctuation and all. There is no hidden formatting layer, no compression and no proprietary structure — which is precisely the point. A Markdown file is readable whether or not you have the right software.

That is the difference from a Word document. A .docx is a zip archive of XML that needs an application to interpret it. An .md file is just characters.

How to open one

Any text editor will open it, because it is text. What most people actually want is to see it formatted — headings rendered as headings, lists as lists — and for that you need something that renders Markdown.

In a browser, on any device — drop the file onto the editor. Nothing is uploaded; the file is read locally.
Windows — Notepad shows the source; VS Code and Obsidian render it.
macOS — TextEdit shows the source; MacDown and iA Writer render it.
Phones — the browser route works everywhere, which is usually the fastest option.

Windows and macOS both associate .md with a plain text editor by default, so double-clicking shows the raw punctuation rather than an error. That is not the file being broken.

.md, .markdown, .mdown

All the same format. .md is shortest and by far the most common. Tools treat every one of these extensions identically, so renaming between them changes nothing.

Where you will run into them

README files in software projects are Markdown, which is why nearly every repository has a README.md. Static site generators, note apps like Obsidian, documentation systems and chat tools all use it. So do large language models: when ChatGPT or Claude replies with headings and bullet points, it is writing Markdown, which is why pasting that reply somewhere often leaves stray asterisks behind.

Converting it to something else

Open the file in the editor and use Export. PDF, Word and standalone HTML all convert in your browser, so the document never leaves your device — worth knowing if it is a contract or an unpublished draft.

Common questions

What does MD stand for?: Markdown. The .md extension marks a plain text file written in Markdown, a lightweight way of adding formatting — headings, lists, links, emphasis — using ordinary punctuation.
What is an .md file?: A plain text file whose contents follow Markdown conventions. There is nothing binary or proprietary inside it: open it in Notepad or TextEdit and you see exactly what the author typed, punctuation and all.
How do I open an .md file?: Any text editor opens it, because it is text. To see it formatted rather than raw you need something that renders Markdown — this site does that in your browser, with no install and no upload.
What is the difference between .md and .markdown?: Nothing. Both extensions mean the same thing and every tool treats them identically. .md is shorter and far more common; .mdown and .mkd also appear occasionally.
Can I convert an .md file to Word or PDF?: Yes. Open it here and export to PDF, Word or HTML from the Export menu. All three conversions run in your browser, so the file is never uploaded.
Why is Markdown used so widely?: Because the source stays readable. A Markdown file is legible as plain text, diffs cleanly in version control, and will still open in fifty years — none of which is true of a binary word processor format. It is also the format large language models write in by default.