> For the complete documentation index, see [llms.txt](https://guides.clickatell.com/flow/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guides.clickatell.com/flow/action-nodes/action-nodes-wait-for-callback.md).

# Wait For Callback

The *Wait for Callback* node is used to facilitate an asynchronous process external to Chat Flow and continue the flow when a callback is received.

This node will block the flow until a callback is received or the session times out.

{% hint style="info" %}
To use this node, the [Wait For Callback API](https://help.clickatell.com/developers-api-reference/wait-for-callback) needs to be set up.
{% endhint %}

{% hint style="warning" %}
This node must be used in conjunction with the [*Set Variables*](/flow/action-nodes/action-nodes-set-variables.md) node. The *Reference* that is being set is the variable from the *Set Variable* node.
{% endhint %}

<figure><img src="/files/TI3EyINZy5V9LyatVQrR" alt=""><figcaption><p>Setup of a Wait For Callback node</p></figcaption></figure>

<figure><img src="/files/DSR7LcxbLh7u7PtGaN6c" alt=""><figcaption><p>Example flow containing Wait For Callback node</p></figcaption></figure>