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

# SIP headers

> Forward custom SIP headers from a Vobiz SIP endpoint to your application - configure your SIP phone to send headers and access them in the HTTP request.

If you're using a SIP endpoint and you've configured your SIP phone to send custom SIP headers starting with X-VH-, Vobiz will send these SIP headers with the HTTP request.

## Outbound calls

For outbound calls, you can set custom SIP headers while:

* Making an outbound call

  * Using the nested Number element of the Dial element

  * Using the nested User element of the Dial element

## Inbound calls

For inbound calls, you need a SIP phone that allows custom SIP headers. If you have one, SIP headers that start with X-VH- will sent as HTTP requests.