# DocumentOutlineConfig

interface

The configuration of the [document outline feature](module_document-outline_documentoutline-DocumentOutline.md).

```typescript
ClassicEditor
	.create( {
		documentOutline:  ... // Document outline feature configuration.
	} )
	.then( /* ... */ )
	.catch( /* ... */ );
```

See [all editor options](module_core_editor_editorconfig-EditorConfig.md).

<a id="properties">

## Properties

<a id="member-container">

### `container?: HTMLElement`

The container element for the document outline to render. This should be a reference to an existing container element in the DOM.

<a id="member-headings">

### `headings?: Array<string>`

An array of [model](../framework/architecture/editing-engine.md#model) element names considered as headings in the document outline.

The index of the heading in the array reflects the heading nesting level. It can be used e.g. for reducing the number of visible headings.

```typescript
ClassicEditor
	.create( {
		plugins: [ DocumentOutline, /* ... */ ],
		documentOutline: {
			headings: [ 'heading1', 'heading2', /* ... */ ],
			// ...
		}
	} )
	.then( /* ... */ )
	.catch( /* ... */ );
```

If this configuration is not defined, the feature will use the following defaults instead:

1. If the [Headings feature](../features/headings.md) is loaded, it equals

* [`config.heading.options`](module_heading_headingconfig-HeadingConfig.md#member-options).
* `[ 'heading1', 'heading2', 'heading3' ]` if `config.heading.options` is not defined.

2. If the [General HTML Support](../features/html/general-html-support.md) feature is loaded, it equals `[ 'htmlH1', 'htmlH2', 'htmlH3', 'htmlH4', 'htmlH5', 'htmlH6' ]`.

**Note**: The Headings feature takes precedence over the General HTML Support feature when both are loaded.

<a id="member-showEmptyHeadings">

### `showEmptyHeadings?: boolean`

Allows you to display a placeholder text: \[Empty heading] for empty headings.

By default, the display of a placeholder is disabled. To enable it, set this parameter to true.

**Note**: This setting also affects Table of contents feature.

---

Full index of the CKEditor 5 API reference: [llms.txt](llms.txt)