READMEs, documentation, chat messages, AI prompts, static-site blogs — Markdown is the formatting language underneath most of the technical web. Its entire pitch fits in one sentence: readable as plain text, renderable as rich documents, with syntax you can learn in ten minutes.

The core syntax

Headings are # symbols, emphasis is *asterisks* or **double**, links are [text](url), and code is `backticks`. Lists, blockquotes (>), and horizontal rules round out the basics. That's genuinely most of it — the original spec fits on a couple of pages, and a beginner who knows headings, links, lists, and code fences can write 95% of real-world documents.

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Why it won

  • It's plain text. Markdown files diff cleanly in version control, open in any editor, survive decades without proprietary software, and work identically on every platform. No binary formats, no lock-in, no "which app opens this."
  • It's writable at speed. No mouse, no toolbar, no formatting dialogues. Fingers stay on the keyboard and thoughts stay in order — which is why it dominates notes, issues, and chat.
  • It's the AI interchange format. Language models read and write Markdown fluently, making it the natural medium for prompts, generated docs, and agent-produced content. Plain-text-plus-structure is exactly what both humans and models parse best.

Flavors and extensions

Strictly speaking there's no single Markdown — there's the original, CommonMark (the rigor-minded spec), and GitHub-Flavored Markdown (GFM), which adds tables, task lists, strikethrough, and autolinked URLs. GFM is the de facto standard for developer writing. Extended flavors add footnotes, definition lists, and math — check which flavor your renderer supports before using exotic syntax.

Preview as you write

Markdown rewards a live feedback loop: type the syntax, watch the rendered output, adjust. The Markdown previewer renders your text instantly in the browser — nothing uploads, so drafts stay private. Write the README, preview it, ship it.