Embeds

Where this works — prose & API docs. Author an embed in prose with the ```iframe fence, or from a source comment with the @iframe block tag. Both share one config grammar.

An embed is a sandboxed <iframe> — a CodePen, a StackBlitz, a live demo, a video. The theme gives you two ways to author one, and they share one config grammar:

• in prose (README, tutorials, the docs directory) — a ```iframe fenced code block;
• in source comments — the @iframe <url> key=value doc-comment block tag.

Both parse through parseEmbedConfig in embed.ts and become the same <Embed> island (Embed.tsx).

The config grammar

The config is a single line (the fence body may span lines, but tokens are whitespace-delimited):

<url> key=value key="value with spaces" flag

• The first whitespace-delimited token is the URL (required).
• Every token after it is a key=value pair.
• Values may be wrapped in single or double quotes, and a quoted value may contain spaces.
• A bare token with no = is treated as a true flag, but only for boolean keys; any other bare token warns and is ignored.

URL schemes

For security, parseEmbedConfig accepts only https:// URLs or protocol-relative // URLs. Anything else — http://, a relative path, an empty string, or a missing URL — makes the parser return null, and the embed is dropped (the parser logs a warning). See the src.startsWith('https://') || src.startsWith('//') check in embed.ts.

Options

Unknown keys warn and are ignored; the embed still renders. The default sandbox is allow-scripts allow-same-origin allow-popups allow-forms.

Theme syncing — themed and the {theme} token

themed is on by default; pass themed=false to opt out. When on, the embed re-points itself whenever the page theme flips, picking one mechanism in priority order (resolveSrc in Embed.tsx):

1. a literal {theme} token in the URL is replaced with light / dark;
2. an author-declared theme-id query param is left untouched (it wins);
3. otherwise ?theme-id=<theme> is appended automatically.

So https://example.com/demo?ui={theme} becomes …?ui=dark in dark mode. Only a literal themed=false (case-insensitive) disables this — anything else, including omitting it, keeps it on.

Authoring form 1 — the ```iframe prose fence

In any README / tutorial / docs page, write a fenced block with the info string iframe. The body is the config:

```iframe
https://example.com/embed/demo title="Live demo" height=420
```

The fence is lowered to <Embed> by resolveEmbedFences in guide-view.ts. A valid config becomes the embed; an invalid one (e.g. a non-https URL) is dropped. All other fences (js, ts, sh, …) are untouched.

Here is a real, themed embed rendered from a fence:

Authoring form 2 — the @iframe doc-comment tag

In source comments, use the @iframe block tag. Same grammar — first token URL, then key=value:

/**
 * A live demo of the renderer.
 *
 * @iframe https://example.com/embed/demo title="Renderer demo" aspectRatio=16/9
 */
export function render() {}

@iframe is handled by embedBlocks in doclet.ts. Each valid @iframe becomes an <Embed>; the block renders after the symbol's @example section. You can have more than one @iframe on a doclet.

@iframe is not a tag base JSDoc knows, so your config must set tags.allowUnknownTags: true in jsdoc.json (this site's jsdoc.json does). Without it, JSDoc drops the tag before the theme ever sees it.

Under the hood

parseEmbedConfig produces an EmbedSpec; the embed builder in builders.ts emits a self-closing <Embed src="…" …/> MDX JSX node (numbers/booleans stringified, undefined fields omitted so the component applies its defaults). rang registers Embed in mdx-components.tsx; the component renders a data-island="embed" marker that dwar's loader hydrates. Both the live iframe and the click-to-load poster work with no JavaScript (a <noscript> fallback iframe is included).

See also

• Custom tags — @iframe alongside @category / @order, and the allowUnknownTags requirement.
• Callouts, Steps, Tabs — the other authoring primitives.