# Add HTTP Header

## Contents
Overview Configuration

## Overview
The Enterprise Gateway can add HTTP headers to a message as it passes through a policy. It can also set a Base64-encoded value for the header. For example, you can use the Add HTTP Header filter to add a message ID to an HTTP header. This message ID can then be forwarded to the destination Web Service, where messages can be indexed and tracked by their IDs. In this way, you can create a complete audit trail of the message from the time it is received by the Enterprise Gateway, until it is processed by the back-end system. Each message being processed by the Enterprise Gateway is assigned a unique transaction ID, which is stored in the `id` message attribute. You can use the `${id}` property to represent the value of the unique message ID. At runtime, this property is expanded to the value of the `id` message attribute.
## Configuration
To configure the Add HTTP Header filter, complete the following fields: Name: Enter an appropriate name for the filter. HTTP Header Name: Specify the name of the HTTP header to add to the message. HTTP Header Value: Enter the value of the new HTTP header. You can enter properties to represent message attributes. At runtime, the Enterprise Gateway expands these properties to the current value of the corresponding message attribute. For example, the `${id}` property is replaced by the value of the current message ID. Properties have the following syntax: `${messsage_attribute}` Base64 Encode: Select this checkbox to Base64 encode the HTTP header value. For example, you should use this if the header value is an X.509 certificate. Add header to body: Select this radio button to add the HTTP header to the message body. Add header to HTTP headers attribute: Select this radio button to add the HTTP header to the `http.headers` message attribute.