> For the complete documentation index, see [llms.txt](https://docs.2checkout.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.2checkout.com/api-reference/reference/authentication.md).

# Authentication

To authenticate to the 2Checkout REST API include a header with the following structure into your requests:

**X-Avangate-Authentication: code="{VENDOR\_CODE}" date="{REQUEST\_DATE\_TIME}" hash="{HASH}" algo="{ALGO}"**

* **VENDOR\_CODE**: Your unique 2Checkout supplied merchant code.
* **REQUEST\_DATE\_TIME**: The **UTC** date time of the request. Format: **YYYY-MM-DD HH:MM:SS**. You must provide the time of the request in the **GMT** timezone.
* **HASH**: The hashmac digest with a SHA2/SHA3 hashing algorithm of the following: LEN(VENDOR\_CODE) + VENDOR\_CODE + LEN(REQUEST\_DATE\_TIME) + REQUEST\_DATE\_TIME. Use the **secret key** associated with your account for the hashing.

You must authenticate for all requests.


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## Querying This Documentation
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```
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```

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