> ## Documentation Index
> Fetch the complete documentation index at: https://developers.smarterservices.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Block Replacement

> A block that serves as a placeholder for dynamic content

## Basic Example

```json theme={null}
{
  "type": "block_replacement",
  "ref": "sample-ref"
}
```

## Properties

<ParamField path="type" type="string" required="true">
  Identifies this as a replacement block

  Must be <code>block\_replacement</code>
</ParamField>

<ParamField path="ref" type="string" required="true">
  Reference key to look up in the replacements object
</ParamField>

<ParamField path="default" type="undefined" required="false">
  Default content to display if the replacement is not found

  **Accepts:** object, array
</ParamField>

## Usage Notes

* This element is part of the BlockKit system for building dynamic user interfaces
* All properties marked as **(required)** must be included in your JSON structure
* Optional properties can be omitted and will use their default values when applicable