Markdown Preview

Text formatting

# Heading 1
## Heading 2
### Heading 3

**bold text**
*italic text*
~~strikethrough~~
`inline code`

> blockquote
> spans multiple lines

---  (horizontal rule)

Lists

- Unordered item
- Another item
  - Nested item

1. Ordered item
2. Second item
   1. Nested ordered

- [ ] Task list (GFM)
- [x] Completed task

Links and images

[link text](https://example.com)
[link with title](https://example.com "Tooltip")
![alt text](image.png)
![alt text](image.png "Image title")

<https://autolink.example.com>
<email@example.com>

Code blocks

```javascript
const x = 1;
console.log(x);
```

    Indented code block (4 spaces)

Tables (GFM)

| Column 1 | Column 2 | Column 3 |
| -------- | :------: | -------: |
| left     | center   |    right |
| data     | data     |     data |

CommonMark

The strict, unambiguous reference spec. All modern parsers (markdown-it, commonmark.js, marked, rehype) follow this. The base layer everyone agrees on.

GitHub Flavored Markdown (GFM)

CommonMark + GitHub-specific extensions: tables, task lists [ ] / [x], strikethrough ~~text~~, autolinks, emoji shortcodes:smile:, footnotes. The de facto standard for code documentation. Most tools accept GFM.

MDX

Markdown + JSX. Lets you embed React components inside Markdown. Used by Docusaurus, Next.js docs, Astro. Powerful for interactive docs, but breaks compatibility with non-React tooling.

Pandoc Markdown

The "kitchen sink" flavor — adds: math ($E = mc^2$), citations ([@smith2020]), definition lists, fenced divs, and many academic-friendly features. Used for academic papers and books converted to PDF.

Obsidian / Logseq / Roam

Personal knowledge management apps add wikilinks [[Page Name]], block references, embeds, callouts. Increasingly important as note-taking conventions but not portable to other tools.

Compatibility tip

For maximum portability, stick to CommonMark + basic GFM (tables, task lists). Avoid wikilinks and proprietary extensions when content needs to move between tools.

Does this support all Markdown features?

Yes for CommonMark + most GFM: headings, bold, italic, strikethrough, links, images, code blocks (fenced and indented), inline code, blockquotes, ordered/unordered lists, tables, horizontal rules, task lists. Math ($$) and footnotes require dedicated tools (KaTeX, remark-math).

Is the HTML output safe?

The HTML is sanitized via DOMPurify to remove <script> tags, onclick handlers, javascript: URLs, and other XSS vectors before rendering. Safe for displaying user- submitted Markdown.

Why does my Markdown render differently on different sites?

Different flavors. GitHub, Stack Overflow, Discord, and Notion each implement slightly different supersets. For portability, write to CommonMark and avoid extensions unless you control the rendering target.

Can I include HTML inside Markdown?

Yes — Markdown allows raw HTML by design. Block-level HTML elements work inline. Useful when Markdown's vocabulary is too limited (custom CSS classes, complex tables, embedded iframes). Sanitization may strip some tags depending on the parser config.

What's the file extension — .md or .markdown?

Both work. .md is the de facto standard (shorter). .markdown is the original extension Gruber used. GitHub recognizes both.

How do I embed videos or interactive content?

Plain Markdown doesn't have video tags. Most renderers accept HTML iframe / video tags inline. For React-based sites, use MDX to embed components. For static sites, shortcodes (Hugo, Jekyll plugins) provide {% youtube ID %} style syntax.