---
title: DocumentationExtension
framework: docc
role: symbol
role_heading: Directive
path: docc/documentationextension
---

# DocumentationExtension

Defines whether the content in a documentation extension file replaces in-source documentation or amends it (the default).

## Declaration

```swift
@DocumentationExtension(mergeBehavior: Behavior)
```

## Parameters

- `mergeBehavior`: A value of override to replace the in-source documentation with the extension file’s content. (required)

## Mentioned in

Adding Supplemental Content to a Documentation Catalog

## Overview

Overview By default, content from the documentation-extension file is added after the content from the in-source documentation for that symbol. Swift framework and package APIs are typically documented using comments that reside in-source, alongside the APIs themselves. In some cases, you may wish to supplement or replace in-source documentation with content from dedicated documentation extension files. To learn about this process, see Adding Supplemental Content to a Documentation Catalog. Place the DocumentationExtension directive within a Metadata directive in a documentation extension file. Set the mergeBehavior parameter to append or override to indicate whether the extension file’s content amends or replaces the in-source documentation. @Metadata {     @DocumentationExtension(mergeBehavior: override) } note: You can specify a append merge behavior but it has the same effect as not defining a @DocumentationExtension and results in a warning. Containing Elements The following items can include a documentation extension element: Metadata