Markdown, Code Highlighting, and Footnotes

lightpaper.org renders Markdown to HTML using markdown-it with GFM (GitHub Flavored Markdown) extensions, Pygments syntax highlighting, and nh3 HTML sanitization. This gives you a rich set of formatting options while keeping everything secure.

This post covers every supported Markdown feature with examples.

Basic Formatting

Standard Markdown formatting works as expected:

Bold with **double asterisks**
Italic with *single asterisks*
Strikethrough with ~~double tildes~~
Inline code with `backticks`
Links with [text](url)

These are the building blocks. Most documents use all of them.

Headings

Six levels of headings are supported:

# Heading 1
## Heading 2
### Heading 3
#### Heading 4
##### Heading 5
###### Heading 6

Headings are extracted for the table of contents and used by the quality scoring algorithm. Using 3 or more headings earns the maximum structure points for heading hierarchy.

In the paper format, headings are automatically numbered (1, 1.1, 1.2, 2, etc.) to provide the academic section numbering readers expect.

Code Blocks

Fenced code blocks with language identifiers get full Pygments syntax highlighting. Over 500 languages are supported.

```python
def publish(title, content):
    response = httpx.post(
        "https://lightpaper.org/v1/publish",
        json={"title": title, "content": content}
    )
    return response.json()
```

This renders with syntax-highlighted colors for keywords, strings, functions, and other language elements.

Supported Languages

Some commonly used languages:

Language	Identifier	Language	Identifier
Python	`python`	JavaScript	`javascript` or `js`
TypeScript	`typescript` or `ts`	Rust	`rust`
Go	`go`	Java	`java`
C/C++	`c` / `cpp`	SQL	`sql`
Bash	`bash` or `shell`	JSON	`json`
YAML	`yaml`	HTML	`html`
CSS	`css`	Markdown	`markdown`

If no language is specified, Pygments attempts to guess the language from the content. For the most reliable highlighting, always specify the language.

Code blocks contribute to the substance component of the quality score. Including 4+ code blocks earns 5 substance points, and 2-3 blocks earn 3 points.

Tables

GFM-style tables are fully supported:

| Feature | Supported |
|---------|-----------|
| Tables | Yes |
| Alignment | Yes |
| Nested formatting | Yes |

Tables support column alignment with colons:

| Left | Center | Right |
|:-----|:------:|------:|
| a    |   b    |     c |

Tables are wrapped in a scrollable container on mobile devices, so wide tables remain usable on small screens. Including tables in your content adds up to 4 points to your substance score.

Task Lists

GFM task lists render as checkboxes:

- [x] Create an account
- [x] Publish first document
- [ ] Verify LinkedIn
- [ ] Submit credentials

This renders as an interactive-looking checklist (the checkboxes are read-only in the rendered output). Task lists are useful for tutorials, checklists, and project status updates.

Blockquotes

Standard blockquote syntax:

> The web has a publishing problem. Getting words onto a permanent URL
> shouldn't require a CMS or a deployment pipeline.

In the essay format, blockquotes are styled as pull quotes with distinctive typography, making them useful for highlighting key passages.

Nested blockquotes work as well:

> First level
>> Second level
>>> Third level

Footnotes

lightpaper.org supports Markdown footnotes via the markdown-it-footnote plugin:

This claim needs a source[^1]. And so does this one[^2].

[^1]: First reference — https://example.com
[^2]: Second reference with more detail about the source.

Footnotes render as superscript numbers in the text with a numbered footnote section at the bottom of the document. They're essential for academic writing and useful for any content that references external sources.

Footnotes contribute to the attribution score. Three or more footnotes earn 7 points; 1-2 earn 4 points.

Horizontal Rules

Three or more hyphens, asterisks, or underscores on a line:

---

This creates a visual separator between sections.

Images

Standard Markdown image syntax:

![Alt text](https://example.com/image.png "Optional title")

Images are sanitized to allow only http, https, and mailto URL schemes. The alt, title, width, and height attributes are preserved.

Lists

Both ordered and unordered lists are supported, including nested lists:

1. First item
   - Nested bullet
   - Another nested item
2. Second item
3. Third item

- Bullet one
- Bullet two
  1. Nested numbered
  2. Another nested

List items contribute to substance scoring. Five or more list items earn 4 points; 2-4 earn 2 points.

HTML Sanitization

All rendered HTML passes through nh3, a Rust-based HTML sanitizer. This means:

Only whitelisted HTML tags are preserved (headings, paragraphs, links, code, tables, etc.)
JavaScript is stripped entirely — no <script> tags, no onclick handlers, no URLs
Link attributes automatically include rel="noopener noreferrer" for security
CSS style attributes are restricted to safe properties
Only http, https, and mailto URL schemes are allowed

This means you can't embed arbitrary HTML, but it also means published content is safe from XSS attacks. The sanitization happens server-side after Markdown rendering, so there's no way to bypass it.

Formatting Tips for Quality

To maximize your quality score through formatting:

Use 3+ headings for structure (10 points)
Include code blocks for substance (up to 5 points)
Add tables where data is tabular (up to 4 points)
Use footnotes for citations (up to 7 attribution points)
Add a References section heading (8 attribution points)
Vary paragraph lengths for natural rhythm (up to 7 structure points)