Markdown Preview

What is Markdown?

Markdown is a lightweight markup language created by John Gruber in 2004. It uses plain-text formatting symbols like asterisks, hashes, and dashes to indicate structure: headings, bold, italic, lists, links, and code blocks. A Markdown previewer renders that plain text into formatted HTML so you can see exactly how the final document will look before publishing. The original Markdown specification is described in Gruber's Daring Fireball documentation, and the format has since been formalized as CommonMark.

Markdown has become the default writing format for developer documentation, README files, static site generators (Jekyll, Hugo, Astro), wikis, and knowledge bases. GitHub, GitLab, Bitbucket, Stack Overflow, Reddit, and Notion all support Markdown natively. Because the source is plain text, Markdown files are trivial to version-control with Git, diff across branches, and merge without conflicts in non-overlapping sections of a file.

A Markdown preview tool parses your input and converts it to HTML in real time. This lets you catch formatting errors, broken links, and unexpected nesting before you commit a file or publish a page. This previewer runs entirely in your browser with no server round-trip, so you can work on private or sensitive documentation without sending content over the network.

Why Use an Online Markdown Previewer?

Writing Markdown in a plain editor without preview means you are guessing at the output. A live previewer closes that feedback loop instantly.

Markdown Preview Use Cases

Markdown Syntax Reference

The table below maps common Markdown syntax to its rendered result and corresponding HTML element. This covers the CommonMark baseline that virtually every Markdown parser supports.

Markdown Flavors Compared

Different platforms extend the original Markdown specification with extra features. Knowing which flavor you are targeting helps you avoid syntax that silently fails in another renderer.

Code Examples: Rendering Markdown Programmatically

When you need to render Markdown inside an application rather than a browser tool, use one of these libraries. Each example converts a Markdown string to an HTML string.

import { marked } from 'marked'

const md = '# Hello\n\nThis is **Markdown**.'
const html = marked(md)
// → "<h1>Hello</h1>\n<p>This is <strong>Markdown</strong>.</p>\n"

// With options
marked.setOptions({ gfm: true, breaks: true })
const gfmHtml = marked('Line one\nLine two')
// → "<p>Line one<br>Line two</p>\n"

import markdown

md = '# Hello\n\nThis is **Markdown**.'
html = markdown.markdown(md)
# → '<h1>Hello</h1>\n<p>This is <strong>Markdown</strong>.</p>'

# With extensions
html = markdown.markdown(md, extensions=['fenced_code', 'tables'])

# Convert a file
with open('README.md') as f:
    html = markdown.markdown(f.read(), extensions=['extra'])

package main

import (
	"bytes"
	"fmt"
	"github.com/yuin/goldmark"
)

func main() {
	source := []byte("# Hello\n\nThis is **Markdown**.")
	var buf bytes.Buffer
	if err := goldmark.Convert(source, &buf); err != nil {
		panic(err)
	}
	fmt.Println(buf.String())
	// → <h1>Hello</h1>
	// → <p>This is <strong>Markdown</strong>.</p>
}

# Convert Markdown file to HTML
pandoc README.md -f markdown -t html -o output.html

# Convert with GitHub Flavored Markdown
pandoc README.md -f gfm -t html --standalone -o output.html

# Pipe from stdin
echo '# Hello **world**' | pandoc -f markdown -t html
# → <h1>Hello <strong>world</strong></h1>

Frequently Asked Questions