Syntax Profile

TanStack Markdown implements a documented subset aimed at repository-authored blogs, guides, API documentation, changelogs, and release notes.

Block syntax

Syntax	Support	Notes
ATX headings	Yes	Levels 1-6 with stable duplicate-safe IDs
Paragraphs	Yes	Soft line breaks remain text line breaks
Fenced code blocks	Yes	Backtick and tilde fences, language and docs metadata
Blockquotes	Yes	Nested parsing with a bounded depth
Unordered lists	Yes	Tight, loose, nested, and task items
Ordered lists	Yes	. and ) markers, custom starts including zero, tight and loose items
Tables	Yes	Header delimiter, alignment, and escaped pipes in cells
Thematic breaks	Yes	Hyphen, asterisk, and underscore forms
Frontmatter extraction	Yes	Leading --- block, enabled by default
Footnotes	Yes	Definition order follows first reference
Raw HTML	Opt-in	Parsed and emitted only with allowHtml: true
Setext headings	No	Use # headings
Indented code blocks	No	Use fenced code blocks

Inline syntax

Syntax	Support	Notes
Emphasis and strong	Yes	Natural prose patterns; not every pathological delimiter case
Strikethrough	Yes	GFM ~~text~~ and legacy TanStack ~text~; numeric approximations stay literal
Inline code	Yes	Matching backtick runs; internal spaces and tabs are preserved
Inline links and images	Yes	Unsafe URL protocols are removed
Reference links and images	Yes	Full, collapsed, and shortcut forms; normalized reference labels
Hard breaks	Yes	Backslash before a newline
Raw inline HTML	Opt-in	Requires allowHtml: true
Autolink literals	Opt-in	HTTP(S) only via the autolinks extension
Entity decoding	Partial	HTML is escaped; full CommonMark entity behavior is not a goal

Docs metadata

Code fences understand metadata used by technical documentation:

markdown

```tsx file="app.tsx" framework="react" {2,4-6}
export function App() {
  return <main>Hello</main>
}
```

The AST records lang, meta, title, file, framework, and highlightLines. Rendering the metadata does not add a syntax highlighter.

Optional docs syntax

The docs extension entry points add:

GitHub-style callouts such as > [!TIP]
heading collection for table-of-contents data
comment-delimited component blocks
file, package-manager, bundler, and framework transforms

See the Docs Preset guide.

Deliberate limits

The following are not project goals:

complete CommonMark or GFM conformance
MDX, JSX parsing, or arbitrary code evaluation
automatic URL linking by default or full GFM autolink conformance
a complete HTML parser or sanitizer
every delimiter, indentation, entity, or reference-label interaction
syntax highlighting, themes, or language grammars
asynchronous plugin pipelines

Unsupported input must still be deterministic and escaped by default. Core parsing limits nesting and inline scans, but does not cap total input size or arbitrary extension work; see Resource limits. New syntax requires evidence from real documentation, regression fixtures, renderer parity, and an accepted bundle cost.