title: “Markdown renderer torture test” description: “CommonMark, GFM, extensions, raw HTML, math, and media” tags: [markdown, rendering, test]

draft: true

Markdown Renderer Torture Test

This document deliberately mixes CommonMark, GitHub Flavored Markdown (GFM), renderer-specific extensions, LaTeX math, and raw HTML. Unsupported syntax should remain readable as source text rather than disappearing.

Table of contents

• Headings
• Inline text
• Links and images
• Lists
• Quotes and callouts
• Code
• Tables
• Math
• Footnotes and references
• Raw HTML
• Escapes and edge cases

Headings

H1: bold, italic, code, link, \(x^2\), and 😀

H2: bold italic, strike, mark, and # escaped hash

H3: bold with nested italic and const x = "#"

H4: bold linked text

H5: H₂O, x², underline

H6: code + strong + emphasis + GFM

Setext H1 with style, code, and link

Setext H2 with emphasis and HTML mark

Heading with a custom ID

The {#custom-heading-id} form is an extension and may render literally.

Inline text

Plain text. Asterisk italic. Underscore italic. Asterisk bold. Underscore bold. Bold italic. Also bold italic. GFM strikethrough. Extension subscript. ^Extension superscript^. ==Extension highlight==. ++Extension insertion++. ||Spoiler extension||.

Nested: bold and italic and struck and code. Overlapping delimiter stress: one two and one *two three*. Intraword underscores should remain: snake_case_name and foobarbaz.

Raw HTML styles: bold, strong, italic, emphasis, underline, strike, deleted, inserted, highlighted, small, H₂O, x², Ctrl+C, sample output, and variable.

Combinations: marked bold italic underlined and bold deleted with H₂O and xⁿ.

Inline code: printf("hello") and code containing a ` backtick.

Two trailing spaces create a hard break.
This line follows a hard break. A backslash also creates one.
This follows the backslash break. This single newline is normally a soft break.

HTML entities: & < > " ' © ® ™   © 🚀.

Unicode: café, naïve, Ελληνικά, Русский, 日本語, 한국어, العربية, עברית, हिन्दी, 😀 🚀 🧪. Combining characters: é versus é. RTL isolate: مرحبا بالعالم. Emoji shortcode extension: :rocket: :warning: :+1:.

Inline CSS style and custom attributes.

Links and images

Links

Inline link, link with title, relative link, fragment link, and encoded URL.

Reference link, numbered reference, collapsed reference, and shortcut-reference.

Autolinks: https://example.com/path?q=test and test@example.com. GFM autolinks: https://example.com and test@example.com.

Potential platform extensions: @octocat, #123, GH-123, and [[Wiki Link]].

Markdown images

Deterministic images use seeded picsum.photos URLs. Sizes range from tiny to large and from extreme panoramas to extreme portraits.

Images inline: between words and at the end.

HTML images with explicit dimensions

Responsive images

Figures, loading, SVG, animation, and failure

Lists

Unordered, ordered, and deeply mixed

• Hyphen item
• Asterisk item
• Plus item

1. First ordered item

2. Second ordered item

3. Third ordered item

4. Ordered list starting at seven

5. Eight

6. Nine

• Level 1 unordered
  1. Level 2 ordered
     • Level 3 unordered

          1. Level 4 ordered
       

       • Level 5 unordered
       • Level 6 with bold, italic, code, and link
         • Level 5 sibling
     • Level 3 sibling
  2. Level 2 sibling
• Level 1 sibling

Tight and loose lists

• Tight item one

• Tight item two

• Tight item three

• Loose item one, first paragraph.

Loose item one, second paragraph with style.

• Loose item two.

A blockquote nested in a list.

The fenced-code variant of this list case is in codeblockstest.md.

| Nested | Table | |:–|–:| | left | right |

Task lists

• [ ] Unchecked task
• [x] Checked task
• [X] Uppercase checked task
• [ ] Parent task
  • [x] Completed child
  • [ ] Pending child
    1. [x] Ordered nested task
    2. [ ] Task with bold, italic, code, and a link

Definition lists (extension)

Markdown

A lightweight markup language.

A second definition for the same term.

Renderer

Software that transforms source syntax into another representation.

List item with indented code

1. Before the code.

   package main

   func main() {}

2. After the code.

Quotes and callouts

A simple blockquote with bold, italic, code, and a link.

A second paragraph.

• A quoted list
  1. A nested ordered item
  2. Another item

Nested quote level two.

Nested quote level three with strike and \(x^2\).

[!NOTE] GitHub-style note alert.

[!TIP] A tip with inline code.

[!IMPORTANT] Important content.

[!WARNING] Warning content.

[!CAUTION] Caution content.

!!! note “Admonition extension” This indented admonition form is used by some Markdown engines.

Indented and HTML code

Four-space indented code:

<div class="not-rendered">Indented HTML-like code</div>
**Markdown is literal here.**

All fenced-code tests live in codeblockstest.md.

Tables

Alignment and inline styles

Left	Center	Right	Default
bold	italic	code	strike
link		\(x^2\)	mark
H2O	x2	Enter	😀
escaped | pipe	a \| b	| entity	underline
bold italic	bold and code	bold link	deleted

Empty, wide, and numeric cells

Images with varied aspect ratios in a table

Square	Landscape	Portrait	Panorama

Multiline and code-block table limitations

Standard pipe-table cells cannot portably contain block elements or fenced code. These alternatives test common renderer behavior:

const answer = 42;

Raw HTML table with a genuine block code cell:

HTML table with rich cell contents

Kind	Rendered content
Code block	.card { display: grid; gap: 1rem; }
Nested list	One Two
Image

Math

Math requires a renderer such as KaTeX or MathJax. Markdown emphasis generally does not apply inside LaTeX; use LaTeX styling commands instead.

Inline forms: \(E = mc^2\), (a^2 + b^2 = c^2), \(\frac{1}{2}\), \(\sqrt[n]{x}\), \(x_i^j\), and \(\mathbf{F} = m\vec{a}\).

Styled surrounding text: Einstein: \(E=mc^2\), Euler: \(e^{i\pi}+1=0\), obsolete guess \(x=0\), and highlighted equation \(y=mx+b\).

LaTeX-internal styles: \(\mathbf{bold}\), \(\mathit{italic}\), \(\mathrm{roman}\), \(\mathsf{sans}\), \(\mathtt{mono}\), \(\mathcal{C}\), \(\mathbb{R}\), \(\boldsymbol{\alpha}\), and \(\color{red}{x^2}\).

Display equation with dollar delimiters:

\[ \int_{-\infty}^{\infty} e^{-x^2}\,dx = \sqrt{\pi} \]

Display equation with bracket delimiters:

[ \sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}{6} ]

Fractions, roots, limits, products, and integrals:

\[ \lim_{x\to 0}\frac{\sin x}{x}=1,\qquad \prod_{k=1}^{n}k=n!,\qquad \sqrt{\frac{-b\pm\sqrt{b^2-4ac}}{2a}} \]

Matrix:

\[ A = \begin{bmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{bmatrix} \]

Cases:

\[ f(x)=\begin{cases} x^2, & x\ge 0, \\ -x, & x<0. \end{cases} \]

Aligned equations:

\[ \begin{aligned} (a+b)^2 &= a^2+2ab+b^2 \\ (a-b)^2 &= a^2-2ab+b^2 \\ (a+b)(a-b) &= a^2-b^2 \end{aligned} \]

Sets, logic, and Greek letters:

\[ \forall x\in\mathbb{R},\; \exists y\in\mathbb{R}: y>x \quad\land\quad \alpha+\beta+\gamma+\Delta+\Omega \]

Escaped currency versus math: The price is $5, while $x$ is literal code and \(\\)x$ tests an escaped dollar inside math.

Footnotes and references

A simple footnote.[^simple] A named footnote with style, code, and a link.[^styled] The same repeated footnote appears again.[^simple] An inline footnote extension may look like this.^[Inline footnote content.]

Multiline footnote reference.[^multiline]

[^simple]: This is a simple footnote.

[^styled]: Footnote with bold, italic, strike, code, \(x^2\), and a link.

[^multiline]: First paragraph of a multiline footnote.

Second paragraph, indented beneath the footnote.

- A nested list item
- Another item with `code`

An indented code-like line inside a footnote.

Abbreviation extension: HTML and CSS are commonly used together.

*[HTML]: HyperText Markup Language *[CSS]: Cascading Style Sheets

Citation extension: Rendering research [@commonmark; @gfm].

Raw HTML

Ruby annotation: 漢(かん)字(じ).

Progress: 67%

Meter: 72

Keyboard sequence: Ctrl + Shift + P.

Description list:

Term

Definition with strong text.

Another term

Another definition.

An HTML blockquote.

Raw HTML preformatted text
  preserves indentation
    and whitespace.

فقرة عربية من اليمين إلى اليسار.

This content should not be visually displayed.

Alternate front matter examples shown literally

The document already begins with YAML front matter. TOML and JSON front matter cannot simultaneously serve as active metadata. Their fenced representations are in codeblockstest.md.

Escapes and edge cases

This is intentionally the final section so escaping failures cannot affect later tests.

Backslash-escapable ASCII punctuation

! \” # $ \% & \’ ( ) * + \, - . \/ : \; < \= > \? \@ [ \ ] ^ _ ` { | } ~

Escaped Markdown examples: *not italic*, _not italic_, *not bold*,
# not a heading, [not a link](https://example.com), `not code`, 1. not a list, - not a list, and > not a quote.

Backslash runs: \ is inline code, \ is two source backslashes, and \* tests odd/even escape behavior before an asterisk.

Escaped entities and URL characters: &amp; \?query\=one&two #fragment \%20.

Ambiguous delimiters and empty constructs

and ` and and and <> and < >.

alpha beta gamma delta

Nested brackets: outer [inner text] still outer.

Nested parentheses in destination: parentheses.

Escaped destination: escaped paren.

Angle destination: spaces allowed in angle destination.

Thematic breaks

Text direction and character stress

LTR then RTL: English before العربية after English.

Directional HTML: ABC אבג 123 XYZ.

CJK without spaces: 日本語の長い文章が改行と折り返しをテストします。

Combining marks: a̐ é ö̲ Z̬̥̮̺̫̖͑ͫ̓ͪ͆ͧ̚̕͘.

Zero-width stress between brackets (the middle pair contains a zero-width space): [] versus [​].

Very long unbroken token:

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789

Deep blockquote stress

Level 1

Level 2

Level 3

Level 4

Level 5

Level 6

Level 7

Level 8

Repeated mixed-style stress

Bold italic code strike link mark H₂O x² \(x^2\)

Escaped terminator stress at end of file: \ * _ # [ ] ( ) { } | ~ `