---
title: "Header Parameters"
source_url: https://docs.rapyd.net/en/header-parameters.html
lang: en
---

# Header Parameters

REST requests and webhooks contain header parameters for authentication of the messages.

The following headers appear in REST requests in the Payments platform:

- `access_key` - Unique access key provided by Rapyd for each authorized user. Required.

  For more information, see [Developers](https://docs.rapyd.net/en/developers.md "Developers").
- `api_version` - see [Versioning for API Methods](https://docs.rapyd.net/en/versioning-for-api-methods.md "Versioning for API Methods").
- `Content-Type` - Indicates that the data appears in JSON format. Required.

  Always set to **application/json**.
- `idempotency` - A unique string to protect against duplicate transactions. Optional.

  For more information, see [Idempotency](https://docs.rapyd.net/en/idempotency.md "Idempotency").
- `salt` - Salt for the request signature. A random string for each request. Recommended length: 8-16 digits, letters and special characters. Required.
- `signature` - Signature calculated for each message individually. Required.

  - For REST requests, see [Request Signatures](https://docs.rapyd.net/en/request-signatures.md "Request Signatures").
  - For webhooks, see [Webhook Authentication](https://docs.rapyd.net/en/webhook-authentication.md "Webhook Authentication").
- `timestamp` - The time of the request, in [Unix time](https://docs.rapyd.net/en/glossary.md#UUID-945d98cf-adae-e1cf-2606-c7fae8b4a7e1_unix_time "Unix time") (seconds). Required.

  The Rapyd platform is synchronized to the actual current time, as defined by public [NTP](https://docs.rapyd.net/en/glossary.md#UUID-945d98cf-adae-e1cf-2606-c7fae8b4a7e1_ntp "Network Time Protocol") servers. The timestamp must be synchronized to the actual current time, or less than 60 seconds before the actual current time.

> **Note:**
>
> In the Point-of-Sale platform, each method has its own headers. See [POS Cash Deposits](https://docs.rapyd.net/en/pos-cash-deposits.md "POS Cash Deposits").