What Is Markdown? A Plain-English Introduction

Markdown in one sentence

Markdown is a way of formatting text using ordinary keyboard symbols, so a plain-text file can be turned into a nicely formatted document — with headings, bold text, lists, links, tables and more.

For example, this Markdown:

# Shopping list

- **Milk**
- Bread
- [Recipe ideas](https://example.com)

…is displayed as a heading, a bulleted list with Milk in bold, and a clickable link. Try it yourself in Markdown Viewer Online.

Why people use Markdown

• It’s just text. A .md file opens on any computer or phone, works with version control like Git, and will still be readable in decades.
• It’s fast to write. You format as you type, without reaching for the mouse.
• It’s portable. The same file can become a web page, a PDF, a Word document or a slide deck.
• It’s everywhere. GitHub, GitLab, Reddit, Discord, Stack Overflow, many note-taking apps and most documentation tools understand Markdown — and AI assistants such as ChatGPT and Claude often reply in it.

A short history

Markdown was created by John Gruber in 2004, with contributions from Aaron Swartz, as a format that is easy to read even before it’s converted. Over time different tools interpreted the rules slightly differently, so in 2014 the CommonMark project published a precise specification. In 2017 GitHub published GitHub Flavored Markdown (GFM), a superset of CommonMark that adds tables, task lists, strikethrough and autolinks. The text/markdown media type was registered in 2016 (RFC 7763).

Markdown Viewer Online supports CommonMark and GFM, plus footnotes, GitHub-style alerts, maths (KaTeX) and diagrams (Mermaid).

The essentials

You type	You get
# Heading	A large heading
**bold**	bold
*italic*	italic
- item	A bulleted list
1. item	A numbered list
[text](https://…)	A link
	An image
`code`	code
> quote	A quotation

The full list is in the Markdown cheat sheet.

Where .md files come from

The most common Markdown file is README.md, the front page of almost every software project. Markdown is also used for documentation sites, wikis, blogs, personal notes and meeting notes. If someone sends you a .md file, see how to open .md files.