Heading anchors

Every heading gets an id so it can be linked. End a heading with {#custom-id} to choose the id yourself, which keeps links stable when the title changes.

Generated ids

The id is the heading text lowercased, with punctuation removed and words joined by single hyphens. Inline markup is ignored. When the same slug appears twice in a document, later headings get -1, -2 and so on in document order.

The headings on this page demonstrate it: this section is generated-ids because of its custom id, while the next heading below gets the slug a-plain-heading.

A plain heading

Open the page source in your browser to see id="a-plain-heading" on the heading above.

Custom ids

A custom id must start with a letter or underscore and may use letters, digits, -, _, : and .. A duplicate custom id, or a malformed one, is a validation error that names the line.

Slug only

## Example 1: Use AI models from any company's AI API

See [the multiplexer](#ai-api-multiplexer) for the next step.

With a custom id

## Multiplexing across vendors {#ai-api-multiplexer}

Links such as [this one](#ai-api-multiplexer) keep working when the title is reworded.

Linking to a section

Link to any heading with a fragment link, for example the generated ids section or custom ids.