Markdown Is Not HTML, But It Was Born to Become It

Markdown is a writing syntax that converts cleanly to HTML. It was designed in 2004 by John Gruber as a simple way to format text that becomes HTML when rendered. Each Markdown construct maps directly to a single HTML element. For example, a title written with # becomes an h1 tag, bold text with ** becomes a strong tag, and a list item with - becomes a list item tag inside an unordered list.

The conversion process is straightforward. A Markdown-to-HTML converter reads the Markdown, understands the structure line by line, and outputs the corresponding HTML tags. No magic is involved, and no server is required. This conversion happens purely through text processing, which is why it can be done instantly in a browser.

GitHub Flavored Markdown, as used by platforms like GitHub and Dev.to, expands upon plain Markdown. It adds support for tables, task lists, and autolinks. A table written with pipes (|) becomes a real HTML table with thead and tbody, rather than a picture of a table. A checklist written with checkmarks becomes a list item with a checked checkbox. And a bare URL becomes a clickable link without any extra syntax.

However, not all Markdown converters handle these additional features. If a converter fails to handle tables, task lists, or autolinks, it is essentially converting 2004 Markdown, not the Markdown used today.

A key safety consideration is that a converter that passes raw HTML through will also pass a script tag. If you paste a document containing a script tag into such a converter and copy the output into your content management system, you could inadvertently ship executable code to your readers. To prevent this, a safe converter should escape source HTML before parsing, ensuring that only tags generated by the parser itself appear in the output.

This is crucial when pasting Markdown written by others into your own site, as it can help prevent malicious code from being executed.