> This page is for Afterpay Online Developer, version Main (default).
> For other versions, use one of these documentation indexes:
> - Main (default): https://developers.afterpay.com/afterpay-online-developer/main/llms.txt
> - v1: https://developers.afterpay.com/afterpay-online-developer/v-1/llms.txt
> - Chinese: https://developers.afterpay.com/afterpay-online-developer/chinese/llms.txt

> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.afterpay.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.afterpay.com/_mcp/server.

# Request headers

Clients must send appropriate headers with all requests.

## HTTP headers

| Field Name    | Requirement | Description                                                                                                |
| ------------- | ----------- | ---------------------------------------------------------------------------------------------------------- |
| Authorization | required    | See [Authentication](/afterpay-online-developer/main/api-reference/reference/introduction/authentication). |
| Content-Type  | required    | All POST and PUT requests must declare the content-type as `application/json`.                             |
| User-Agent    | required    | See below.                                                                                                 |
| Accept        | recommended | All requests must accept `application/json` or `*/*`.                                                      |

## User-Agent header

User-Agent headers are used by the Afterpay team to identify API requests. You can use the following information to help generate your User-Agent header. User-Agent header must be supplied with all Merchant API requests prior to placing any live transactions.

For example: `MyAfterpayModule/1.0.0 (E-Commerce Platform Name/1.0.0; PHP/7.0.0; Merchantname/600032000) https://merchant.example.com`

| Description          | Example Data Above                                           | Other Merchant Examples                                                            |
| -------------------- | ------------------------------------------------------------ | ---------------------------------------------------------------------------------- |
| Afterpay Plugin      | MyAfterpayModule/1.0.0                                       | Custom Plugin/1.0 Shopify Plugin/3.5.1 AfterpayCartridge/1.0 AfterpayExtension/2.9 |
| Platform             | E-Commerce Platform Name/1.0.0                               | Websphere Commerce/8.1 Commerce Cloud/1.1 Adobe Commerce (Magento)/2.3.0           |
| System Information   | PHP/7.0.0                                                    | PHP/7.2.18  Ruby/2.5.3  Java/8.3                                                   |
| Merchant ID          | Merchantname/600032000                                       | Merchantname/101113200 Merchantname/101931210                                      |
| Merchant Website URL | [https://merchant.example.com](https://merchant.example.com) | [http://www.merchantwebsite.com](http://www.merchantwebsite.com)                   |

> **Note**
>
> In this case the Merchant ID is your company name or organization name followed by an eight-digit number.