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

# Receiving Messages

> What do we send to your API?

When you publish a message, QStash will deliver it to your chosen destination. This is a brief overview of how a request to your API looks like.

## Headers

We are forwarding all headers that have been prefixed with `Upstash-Forward-` to your API. [Learn more](/qstash/howto/publishing#sending-custom-http-headers)

In addition to your custom headers, we're sending these headers as well:

| Header                | Description                                                          |
| --------------------- | -------------------------------------------------------------------- |
| `User-Agent`          | Will be set to `Upstash-QStash`                                      |
| `Content-Type`        | The original `Content-Type` header                                   |
| `Upstash-Topic-Name`  | The URL Group (topic) name if sent to a URL Group                    |
| `Upstash-Signature`   | The signature you need to verify [See here](/qstash/howto/signature) |
| `Upstash-Retried`     | How often the message has been retried so far. Starts with 0.        |
| `Upstash-Message-Id`  | The message id of the message.                                       |
| `Upstash-Schedule-Id` | The schedule id of the message if it is related to a schedule.       |
| `Upstash-Caller-Ip`   | The IP address of the publisher of this message.                     |

## Body

The body is passed as is, we do not modify it at all. If you send a JSON body, you will receive a JSON body. If you send a string, you will receive a string.

## Verifying the signature

[See here](/qstash/howto/signature)