Markdown converts plain text with simple syntax into clean HTML. Used in GitHub READMEs, WordPress, Ghost, Hugo, Jekyll, Notion, and Slack. Key syntax: # headings, **bold**, *italic*, [text](url), , - lists, `code`, ```blocks```, > blockquotes, and --- horizontal rules. Our converter outputs semantic HTML with proper heading hierarchy, which is important for SEO. Preview the rendered output before publishing.